func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[1005][1005], i, m, ans, k, l, j, q, x, n, ma, mi;   string s;   int main() {     cin >> n >> k;     if (k >= (n + 1) / 2) {       cout << -1;       return 0;     }     cout << n * k << endl;     for (int i = 1; i <= n; i++) {       int w = k;       for (int j = 1; j <= n; j++) {         if (a[i][j] == 1 || i == j) continue;         cout << i <<     << j << endl;         a[i][j] = 1;         a[j][i] = 1;         w--;         if (!w) break;       }     }   }   