diff --git a/lc_0621_task_scheduler.py b/lc_0621_task_scheduler.py
new file mode 100644
index 0000000..8ebab8e
--- /dev/null
+++ b/lc_0621_task_scheduler.py
@@ -0,0 +1,38 @@
+from collections import Counter
+from itertools import count
+from typing import List
+import unittest
+
+
+class Solution:
+    def leastInterval(self, tasks: List[str], n: int) -> int:
+
+        task_list = [(v, 0) for v in Counter(tasks).values()]
+
+        for time in count():
+            if not task_list:
+                return time
+
+            tx, ix = max(((t, i) for i, (t, b) in enumerate(task_list) if time >= b),
+                         default=(None, None))
+
+            if ix is not None:
+                task_list[ix: ix + 1] = [(tx - 1, time + n + 1)] if tx > 1 else []
+
+
+class MyTestCase(unittest.TestCase):
+    def setUp(self) -> None:
+        self.f = Solution().leastInterval
+
+    def test_examples(self):
+        assert self.f(["A", "A", "A", "B", "B", "B"], 2) == 8
+        assert self.f(["A", "A", "A", "B", "B", "B"], 0) == 6
+        assert self.f(["A", "A", "A", "A", "A", "A", "B", "C", "D", "E", "F", "G"], 2) == 16
+
+    def test_simple(self):
+        assert self.f(["A"], 100) == 1
+        assert self.f(["A", "A"], 100) == 102
+
+
+if __name__ == "__main__":
+    unittest.main()