func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e6 + 5;   int main() {     int n, K;     cin >> n >> K;     if (K == 1 || n <= 3) {       puts( -1 );     } else if (K >= n) {       puts( -1 );     } else if (n == 4) {       if (K == 3) {         puts( 3 n1 2 n2 3 n3 4 );       } else {         puts( -1 );       }     } else {       if (K == 3) {         vector<pair<int, int> > E;         E.push_back({1, 2});         E.push_back({2, 3});         E.push_back({3, 4});         for (int i = 2; i <= 3; ++i) {           for (int j = 5; j <= n; ++j) {             E.push_back({i, j});           }         }         printf( %d n , E.size());         for (auto it : E) {           printf( %d %d n , it.first, it.second);         }       } else if (K == 2) {         printf( %d n , n - 1);         for (int i = 1; i < n; ++i) {           printf( %d %d n , i, i + 1);         }       } else {         puts( -1 );       }     }   }   