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