func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     int f = 0;     int a[502] = {0,   1,   3,   6,   10,  15,  21,  28,  36,  45,  55,                   66,  78,  91,  105, 120, 136, 153, 171, 190, 210, 231,                   253, 276, 300, 325, 351, 378, 406, 435, 465, 496};     for (int i = 0; i < 32; i++) {       if (a[i] == n) {         cout <<  YES ;         f = 1;       }     }     if (f == 0) cout <<  NO ;   }   