question70.cpp

#include<bits/stdc++.h>
using namespace std;

class Solution {
public:
    int pivotInteger(int n) {
        
        int sum = n * (n + 1)/ 2;
        double a = sqrt(sum);

        if(a - ceil(a) == 0)
        {
            return int(a);
        }
        else{
            return -1;
        }

    }
};