func_code_string: #include <bits/stdc++.h>   const int N = 1005;   int n, K;   int w[N][N];   std::vector<int> ansx, ansy;   int main() {     memset(w, -1, sizeof w);     bool f = true;     scanf( %d%d , &n, &K);     for (int i = 1; i <= n; ++i) {       int cnt = K;       for (int j = 1; j <= n && cnt > 0; ++j)         if (j != i && w[i][j] == -1) {           --cnt;           w[i][j] = 1;           w[j][i] = 0;           ansx.push_back(i);           ansy.push_back(j);         }       if (cnt != 0) {         f = false;         break;       }     }     if (!f)       puts( -1 );     else {       printf( %d n , ansx.size());       for (int i = 0; i < ansx.size(); ++i) printf( %d %d n , ansx[i], ansy[i]);     }     return 0;   }   