func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     int n;     scanf( %d , &n);     vector<int> game(n + 1);     game[0] = game[1] = game[2] = 0;     vector<int> res(n + 1, -1);     for (int i = 3; i <= n; i++) {       int ok[300001];       memset(ok, 0, sizeof(0));       for (int j = 2; i - (j * (j - 1)) / 2 >= 0; j++) {         int x = i - ((j) * (j - 1)) / 2;         if (x % j == 0) {           x /= j;           int Xor = 0;           for (int k = 0; k < j; k++) {             Xor ^= game[x + k];           }           ok[Xor] = i;           if (Xor == 0 && res[i] == -1) {             res[i] = j;           }         }       }       int r = 0;       while (ok[r] == i) r++;       game[i] = r;       if (game[i] == 0) res[i] = -1;     }     printf( %d n , res[n]);   }   