diff --git a/challenges/ppc/online_judge/attachments/API.md b/challenges/ppc/online_judge/attachments/API.md
new file mode 100644
index 0000000..043655d
--- /dev/null
+++ b/challenges/ppc/online_judge/attachments/API.md
@@ -0,0 +1,100 @@
+# [PPC] 更适合破晓宝宝的 OJ API 文档
+
+程序只有两个 API ，URL 路径都是 `/jobs`。
+
+GET 请求返回全部已提交的任务，返回它们的状态和结果：
+
+```json
+[
+  {
+    "id": 0,
+    "created_time": "2023-10-16T18:34:16.287Z",
+    "updated_time": "2023-10-16T18:34:16.287Z",
+    "submission": {
+      "source_code": "#include <stdio.h>\nint main() {\nprintf(\"Hello World!\");\nreturn 0;}",
+      "language": "C",
+      "problem_id": 0
+    },
+    "state": "Finished",
+    "result": "Accepted",
+    "cases": [
+      {
+        "result": "Compilation Success",
+        "time": 0,
+        "memory": 0
+      },
+      {
+        "result": "Accepted",
+        "time": 0,
+        "memory": 0
+      }
+    ],
+    "flag": "flag{"
+  }，
+  {
+    "id": 1,
+    "created_time": "2023-10-16T19:41:05.106Z",
+    "updated_time": "2023-10-16T19:41:05.106Z",
+    "submission": {
+      "source_code": "#include <stdio.h>\nint main() {\nprintf(\"Hello World!\");\nreturn }",
+      "language": "C",
+      "problem_id": 0
+    },
+    "state": "Finished",
+    "result": "Compilation Error",
+    "cases": [
+      {
+        "result": "Compilation Error",
+        "time": 0,
+        "memory": 0
+      }
+    ],
+    "flag": ""
+  }
+]
+```
+
+---
+
+POST 请求提交 语言类型、题目 ID 、代码内容 ，返回此次评测结果：
+
+REQUEST：
+
+```json
+{
+    "language": "C",
+    "problem_id": 0,
+    "source_code": "#include <stdio.h>\nint main() {\nprintf(\"Hello World!\");\nreturn 0;}",
+}
+```
+
+RESPONSE：
+
+```json
+{
+  "id": 3,
+  "created_time": "2023-10-16T19:39:33.541Z",
+  "updated_time": "2023-10-16T19:39:33.541Z",
+  "submission": {
+    "source_code": "#include <stdio.h>\nint main() {\nprintf(\"Hello World!\");\nreturn 0;}",
+    "language": "C",
+    "problem_id": 0
+  },
+  "state": "Finished",
+  "result": "Accepted",
+  "cases": [
+    {
+      "result": "Compilation Success",
+      "time": 0,
+      "memory": 0
+    },
+    {
+      "result": "Accepted",
+      "time": 0,
+      "memory": 0
+    }
+  ],
+  "flag": "flag{"
+}
+```
+
diff --git a/challenges/ppc/online_judge/attachments/PROBLEMS.md b/challenges/ppc/online_judge/attachments/PROBLEMS.md
new file mode 100644
index 0000000..c17b2f5
--- /dev/null
+++ b/challenges/ppc/online_judge/attachments/PROBLEMS.md
@@ -0,0 +1,110 @@
+# [PPC] 更适合破晓宝宝的 OJ 题单
+
+每个题目名前的方括号中是题目 ID，如 `[0] 输出 Hello World!`，就代表着这题的 `problem_id` 为 `0`，在提交数据时使用以下 JSON ：
+
+```json
+{
+    "language": "C",
+    "problem_id": 0,
+    "source_code": "#include <stdio.h>\nint main() {\nprintf(\"Hello World!\");\nreturn 0;}",
+}
+```
+
+**注意输出不要携带换行符，大小写敏感**。
+
+## [0] 输出 Hello World!
+
+程序不接受任何输入，只输出 `Hello World!`。
+
+**示例：**
+
+```
+输入：121
+输出：Hello World!
+```
+
+## [1] 回文数
+
+给你一个整数，如果它是一个回文整数，返回 `true` ；否则，返回 `false` 。
+
+回文数是指正序（从左向右）和倒序（从右向左）读都是一样的整数。
+
+- 例如，`121` 是回文，而 `123` 不是。
+
+**示例 1：**
+
+```
+输入：121
+输出：true
+```
+
+**示例 2：**
+
+```
+输入：-121
+输出：false
+解释：从左向右读, 为 -121 。 从右向左读, 为 121- 。因此它不是一个回文数。
+```
+
+**示例 3：**
+
+```
+输入：10
+输出：false
+解释：从右向左读, 为 01 。因此它不是一个回文数。
+```
+
+## [2] 转换成小写字母
+
+给你一个字符串 `s` ，将该字符串中的大写字母转换成相同的小写字母，返回新的字符串。 
+
+**示例 1：**
+
+```
+输入：Hello
+输出：hello
+```
+
+**示例 2：**
+
+```
+输入：here
+输出：here
+```
+
+**示例 3：**
+
+```
+输入：LOVELY
+输出：lovely
+```
+
+## [3] 倍数求和
+
+给你一个正整数 `n` ，请你计算在 `[1，n]` 范围内能被 `3`、`5`、`7` 整除的所有整数之和。
+
+返回一个整数，用于表示给定范围内所有满足约束条件的数字之和。
+
+**示例 1：**
+
+```
+输入：7
+输出：21
+解释：在 [1, 7] 范围内能被 3、5、7 整除的所有整数分别是 3、5、6、7 。数字之和为 21 。
+```
+
+**示例 2：**
+
+```
+输入：10
+输出：40
+解释：在 [1, 10] 范围内能被 3、5、7 整除的所有整数分别是 3、5、6、7、9、10 。数字之和为 40 。
+```
+
+**示例 3：**
+
+```
+输入：9
+输出：30
+解释：在 [1, 9] 范围内能被 3、5、7 整除的所有整数分别是 3、5、6、7、9 。数字之和为 30 。
+```
diff --git a/challenges/ppc/online_judge/attachments/README.md b/challenges/ppc/online_judge/attachments/README.md
new file mode 100644
index 0000000..7d268b8
--- /dev/null
+++ b/challenges/ppc/online_judge/attachments/README.md
@@ -0,0 +1,49 @@
+# [PPC] 更适合破晓宝宝的 OJ 使用指南
+
+OJ 即 OnlineJudge，在线评测系统，用于自动评判编程代码的准确性和效率。
+
+**你的程序要求实现接收特定的内容，并输出对应的正确内容**。
+
+**你提交的代码，会在系统中编译后，根据提交的对应题目进行测试**。
+
+**每道题都有一个或多个测试用例，用于判断你给出的程序的正确性**。
+
+测试用例是的一组文件，分别对应着**程序输入**和**程序该有的输出**。当测试失败时，返回结果中可以看到是哪个测试用例因为什么失败，如答案错误。（不会有测试用例的具体内容）
+
+允许且推荐使用 ChatGPT 以及搜索引擎等工具，因为平台根本没法不允许，也没必要。
+
+当然自己写的代码是最酷的。
+
+不过，想想这题还能怎么做？这可是 CTF。
+
+## FLAG 从哪来 ？
+
+每完成一道题目，会从服务器根目录的 `/flag`文件中返回一部分 FLAG。
+
+每道题的 FLAG 片段都是固定的。
+
+做题顺序不限制，但 FLAG 片段是有序的。
+
+比如第一题，返回的就是 FLAG 第一个片段，第二题就是第二个片段，共四题，组合起来就是完整 FLAG 。
+
+## 怎么做题 ？
+
+系统没有前端页面，只有一个 Web API ，你可以参照 [API 文档](API.md) 中的规范，使用任何可以发送 HTTP 包的工具来调用。
+
+但由于在 JSON 中手写代码会遇到字符转义的痛苦事情，建议自写脚本或使用题目附件中提供的 `judge.py` 。
+
+你需要修改 `judge.py` 中 `localhost` 为你的容器 IP。
+
+修改 `judge.py` 中 `12345` 为你的容器端口。
+
+并根据题目 ID 修改 `judge.py` 中 `problem_id` 为对应题目 ID。
+
+修改 `test.c` 内容为你要提交的代码。
+
+然后运行 `python judge.py`。
+
+`judge.py` 会返回提交过所有任务的结果，而不是只有本次结果，以 JSON 格式显示。
+
+## 语言
+
+语言有两者可选 `C`、`CPP`，需要在 `judge.py` 修改 `language` 为 `"C"` 或 `"CPP"`
diff --git a/challenges/ppc/online_judge/build/config.json b/challenges/ppc/online_judge/build/config.json
index 716d083..873c0b7 100644
--- a/challenges/ppc/online_judge/build/config.json
+++ b/challenges/ppc/online_judge/build/config.json
@@ -18,11 +18,35 @@
     },
     {
       "id": 1,
-      "name": "hello_world",
+      "name": "palindrome_number",
       "cases": [
         {
-          "input_file": "data/hello_world/1.in",
-          "answer_file": "data/hello_world/1.ans",
+          "input_file": "data/palindrome_number/1.in",
+          "answer_file": "data/palindrome_number/1.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/palindrome_number/2.in",
+          "answer_file": "data/palindrome_number/2.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/palindrome_number/3.in",
+          "answer_file": "data/palindrome_number/3.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/palindrome_number/4.in",
+          "answer_file": "data/palindrome_number/4.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/palindrome_number/5.in",
+          "answer_file": "data/palindrome_number/5.ans",
           "time_limit": 2000000,
           "memory_limit": 1048576
         }
@@ -30,11 +54,71 @@
     },
     {
       "id": 2,
-      "name": "hello_world",
+      "name": "to_lower_case",
       "cases": [
         {
-          "input_file": "data/hello_world/1.in",
-          "answer_file": "data/hello_world/1.ans",
+          "input_file": "data/to_lower_case/1.in",
+          "answer_file": "data/to_lower_case/1.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/to_lower_case/2.in",
+          "answer_file": "data/to_lower_case/2.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/to_lower_case/3.in",
+          "answer_file": "data/to_lower_case/3.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/to_lower_case/4.in",
+          "answer_file": "data/to_lower_case/4.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/to_lower_case/5.in",
+          "answer_file": "data/to_lower_case/5.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        }
+      ]
+    },
+    {
+      "id": 3,
+      "name": "sum_multiples",
+      "cases": [
+        {
+          "input_file": "data/sum_multiples/1.in",
+          "answer_file": "data/sum_multiples/1.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/sum_multiples/2.in",
+          "answer_file": "data/sum_multiples/2.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/sum_multiples/3.in",
+          "answer_file": "data/sum_multiples/3.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/sum_multiples/4.in",
+          "answer_file": "data/sum_multiples/4.ans",
+          "time_limit": 2000000,
+          "memory_limit": 1048576
+        },
+        {
+          "input_file": "data/sum_multiples/5.in",
+          "answer_file": "data/sum_multiples/5.ans",
           "time_limit": 2000000,
           "memory_limit": 1048576
         }
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/1.ans b/challenges/ppc/online_judge/build/data/palindrome_number/1.ans
new file mode 100644
index 0000000..f32a580
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/1.ans
@@ -0,0 +1 @@
+true
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/1.in b/challenges/ppc/online_judge/build/data/palindrome_number/1.in
new file mode 100644
index 0000000..5a396e2
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/1.in
@@ -0,0 +1 @@
+121
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/2.ans b/challenges/ppc/online_judge/build/data/palindrome_number/2.ans
new file mode 100644
index 0000000..02e4a84
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/2.ans
@@ -0,0 +1 @@
+false
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/2.in b/challenges/ppc/online_judge/build/data/palindrome_number/2.in
new file mode 100644
index 0000000..0a77e7b
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/2.in
@@ -0,0 +1 @@
+-121
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/3.ans b/challenges/ppc/online_judge/build/data/palindrome_number/3.ans
new file mode 100644
index 0000000..02e4a84
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/3.ans
@@ -0,0 +1 @@
+false
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/3.in b/challenges/ppc/online_judge/build/data/palindrome_number/3.in
new file mode 100644
index 0000000..9a03714
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/3.in
@@ -0,0 +1 @@
+10
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/4.ans b/challenges/ppc/online_judge/build/data/palindrome_number/4.ans
new file mode 100644
index 0000000..f32a580
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/4.ans
@@ -0,0 +1 @@
+true
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/4.in b/challenges/ppc/online_judge/build/data/palindrome_number/4.in
new file mode 100644
index 0000000..bd7a502
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/4.in
@@ -0,0 +1 @@
+1234554321
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/5.ans b/challenges/ppc/online_judge/build/data/palindrome_number/5.ans
new file mode 100644
index 0000000..f32a580
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/5.ans
@@ -0,0 +1 @@
+true
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/palindrome_number/5.in b/challenges/ppc/online_judge/build/data/palindrome_number/5.in
new file mode 100644
index 0000000..0e052aa
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/palindrome_number/5.in
@@ -0,0 +1 @@
+1425923295241
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/1.ans b/challenges/ppc/online_judge/build/data/sum_multiples/1.ans
new file mode 100644
index 0000000..b5045cc
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/1.ans
@@ -0,0 +1 @@
+21
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/1.in b/challenges/ppc/online_judge/build/data/sum_multiples/1.in
new file mode 100644
index 0000000..c793025
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/1.in
@@ -0,0 +1 @@
+7
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/2.ans b/challenges/ppc/online_judge/build/data/sum_multiples/2.ans
new file mode 100644
index 0000000..86ee83a
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/2.ans
@@ -0,0 +1 @@
+40
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/2.in b/challenges/ppc/online_judge/build/data/sum_multiples/2.in
new file mode 100644
index 0000000..9a03714
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/2.in
@@ -0,0 +1 @@
+10
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/3.ans b/challenges/ppc/online_judge/build/data/sum_multiples/3.ans
new file mode 100644
index 0000000..8580e7b
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/3.ans
@@ -0,0 +1 @@
+30
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/3.in b/challenges/ppc/online_judge/build/data/sum_multiples/3.in
new file mode 100644
index 0000000..f11c82a
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/3.in
@@ -0,0 +1 @@
+9
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/4.ans b/challenges/ppc/online_judge/build/data/sum_multiples/4.ans
new file mode 100644
index 0000000..5160788
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/4.ans
@@ -0,0 +1 @@
+307
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/4.in b/challenges/ppc/online_judge/build/data/sum_multiples/4.in
new file mode 100644
index 0000000..3e932fe
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/4.in
@@ -0,0 +1 @@
+34
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/5.ans b/challenges/ppc/online_judge/build/data/sum_multiples/5.ans
new file mode 100644
index 0000000..7179a19
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/5.ans
@@ -0,0 +1 @@
+964
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/sum_multiples/5.in b/challenges/ppc/online_judge/build/data/sum_multiples/5.in
new file mode 100644
index 0000000..4800c7d
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/sum_multiples/5.in
@@ -0,0 +1 @@
+58
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/1.ans b/challenges/ppc/online_judge/build/data/to_lower_case/1.ans
new file mode 100644
index 0000000..b6fc4c6
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/1.ans
@@ -0,0 +1 @@
+hello
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/1.in b/challenges/ppc/online_judge/build/data/to_lower_case/1.in
new file mode 100644
index 0000000..5ab2f8a
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/1.in
@@ -0,0 +1 @@
+Hello
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/2.ans b/challenges/ppc/online_judge/build/data/to_lower_case/2.ans
new file mode 100644
index 0000000..60aecbd
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/2.ans
@@ -0,0 +1 @@
+here
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/2.in b/challenges/ppc/online_judge/build/data/to_lower_case/2.in
new file mode 100644
index 0000000..60aecbd
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/2.in
@@ -0,0 +1 @@
+here
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/3.ans b/challenges/ppc/online_judge/build/data/to_lower_case/3.ans
new file mode 100644
index 0000000..1940f2b
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/3.ans
@@ -0,0 +1 @@
+lovely
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/3.in b/challenges/ppc/online_judge/build/data/to_lower_case/3.in
new file mode 100644
index 0000000..f6167d5
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/3.in
@@ -0,0 +1 @@
+LOVELY
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/4.ans b/challenges/ppc/online_judge/build/data/to_lower_case/4.ans
new file mode 100644
index 0000000..0f6addb
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/4.ans
@@ -0,0 +1 @@
+he110 world
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/4.in b/challenges/ppc/online_judge/build/data/to_lower_case/4.in
new file mode 100644
index 0000000..4d2cb0c
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/4.in
@@ -0,0 +1 @@
+HE110 WORLD
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/5.ans b/challenges/ppc/online_judge/build/data/to_lower_case/5.ans
new file mode 100644
index 0000000..7221b47
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/5.ans
@@ -0,0 +1 @@
+l41n_w1red_w0rld
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/data/to_lower_case/5.in b/challenges/ppc/online_judge/build/data/to_lower_case/5.in
new file mode 100644
index 0000000..16ffca0
--- /dev/null
+++ b/challenges/ppc/online_judge/build/data/to_lower_case/5.in
@@ -0,0 +1 @@
+L41n_W1red_W0rld
\ No newline at end of file
diff --git a/challenges/ppc/online_judge/build/init.sh b/challenges/ppc/online_judge/build/init.sh
index 735485b..1dcd4dd 100644
--- a/challenges/ppc/online_judge/build/init.sh
+++ b/challenges/ppc/online_judge/build/init.sh
@@ -3,6 +3,4 @@
 echo $GZCTF_FLAG > /flag
 chmod 444 /flag
 
-unset GZCTF_FLAG
-
-/app/oj --config /app/config.json
\ No newline at end of file
+/app/oj --config /app/config.json
diff --git a/challenges/ppc/online_judge/build/src/job.rs b/challenges/ppc/online_judge/build/src/job.rs
index 28da59d..6043353 100644
--- a/challenges/ppc/online_judge/build/src/job.rs
+++ b/challenges/ppc/online_judge/build/src/job.rs
@@ -9,17 +9,12 @@ use std::{
     time::Duration,
 };
 use std::string::ToString;
-use lazy_static::lazy_static;
 use wait_timeout::ChildExt;
 
 use crate::config::Language;
 use crate::{config, AppError, CaseResult, Response, RunResult, State};
 
 const TEMP_DIR_PREFIX: &str = "/tmp";
-lazy_static! {
-    static ref FLAG: String = env::var("GZCTF_FLAG").unwrap_or("flag{test_flag}".to_string());
-    static ref FLAG_LENGTH: usize = FLAG.len();
-}
 
 // the struct represent the json content from the post job http request
 #[derive(Debug, Serialize, Deserialize, Clone)]
@@ -208,11 +203,17 @@ impl Job {
         }
 
         // 返回部分 FLAG
+        let flag: String = env::var("GZCTF_FLAG").unwrap_or("flag{test_flag}".to_string());
+        let flag_length = flag.len();
+
         let problem_count = config.problems.len();
-        let flag_chunk_size = *FLAG_LENGTH / problem_count;
-        let start = (problem.id % problem_count) * flag_chunk_size;
-        let end = start + flag_chunk_size;
-        self.flag = FLAG[start..end].to_string();
+        let flag_chunk_size = flag_length / problem_count;
+        let start = problem.id * flag_chunk_size;
+        let mut end = start + flag_chunk_size;
+        if problem.id == problem_count - 1 {
+            end += flag_length % problem_count;
+        }
+        self.flag = flag[start..end].to_string();
 
         self.state = State::Finished;
         Ok(self.response())
diff --git a/challenges/ppc/online_judge/writeup/palindrome_number.c b/challenges/ppc/online_judge/writeup/palindrome_number.c
new file mode 100644
index 0000000..c6c188a
--- /dev/null
+++ b/challenges/ppc/online_judge/writeup/palindrome_number.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <string.h>
+
+int main() {
+    char buf[100];
+    scanf("%99s", buf);
+
+    int length = strlen(buf);
+    int ptr_left = 0;
+    int ptr_right = length - 1;
+
+    while (ptr_right > ptr_left) {
+        if (buf[ptr_left] != buf[ptr_right]) {
+            printf("false");
+            return 0;
+        }
+        ptr_left++;
+        ptr_right--;
+    }
+
+    printf("true");
+    return 0;
+}
+
diff --git a/challenges/ppc/online_judge/writeup/sum_multiples.c b/challenges/ppc/online_judge/writeup/sum_multiples.c
new file mode 100644
index 0000000..03aaa40
--- /dev/null
+++ b/challenges/ppc/online_judge/writeup/sum_multiples.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <string.h>
+
+int main() {
+    int num;
+    int result = 0;
+
+    scanf("%d", &num);
+
+    for (int i = 0; i <= num; i++) {
+        if (i % 3 == 0 ||  i % 5 == 0 || i % 7 == 0) {
+            result += i;
+        }
+    }
+    printf("%d", result);
+
+    return 0;
+}
+
diff --git a/challenges/ppc/online_judge/writeup/to_lower_case.c b/challenges/ppc/online_judge/writeup/to_lower_case.c
new file mode 100644
index 0000000..8203d89
--- /dev/null
+++ b/challenges/ppc/online_judge/writeup/to_lower_case.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <string.h>
+
+int main() {
+    char s[100];
+
+    fgets(s, sizeof(s), stdin);
+
+    int len = strlen(s);
+    for (int i = 0; i < len; ++i) {
+        if (s[i] >= 65 && s[i] <= 90) {
+            s[i] |= 32;
+        }
+    }
+    printf("%s", s);
+    return 0;
+}
+