func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     int sum = 0;     bool ok = false;     for (int i = 1; i <= n; i++) {       sum = i + sum;       if (n == 1 || n == sum) {         cout <<  YES  << endl;         break;       }       if (sum > n) {         ok = true;         break;       }     }     if (ok) cout <<  NO  << endl;     return 0;   }   