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