func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, k, m;     cin >> n >> k;     m = n * (n - 1) / 2;     if ((double)k > ((double)n - 1) / 2) {       cout << -1;       return 0;     } else {       cout << k * n << endl;       for (int i = 1; i <= n; ++i) {         for (int j = 0; j < k; ++j) {           cout << i <<     << (i + j) % n + 1 << endl;         }       }     }     return 0;   }   