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