func_code_string: #include <bits/stdc++.h>   using namespace std;   int num, sg[100010], mex[100010], col = 1, ans = -1;   int main() {     scanf( %d , &num);     for (int n = 3; n <= num; n++) {       for (int m = 2;; m++) {         int res = n - (m - 1) * m / 2;         if (res < 0) break;         if (res % m) continue;         int g = 0, x = res / m;         for (int i = 0; i < m; i++) g ^= sg[x + i];         if (!g && num == n && ans < 0) {           ans = m;           break;         }         mex[g] = col;       }       for (int j = 0;; j++)         if (mex[j] != col) {           sg[n] = j;           ++col;           break;         }     }     printf( %d , ans);   }   