func_code_string: #include <bits/stdc++.h>   using namespace std;   struct Timer {     Timer() { beg = clock(); }     ~Timer() {}     clock_t beg;   };   int main() {     ios_base::sync_with_stdio(false);     int n, d, h;     cin >> n >> d >> h;     if (d < h) {       cout << -1 << endl;       return 0;     }     if (d == 1 && h == 1) {       if (n == 2) {         cout << 1 <<     << 2 << endl;       } else {         cout << -1 << endl;       }       return 0;     }     if (2 * h < d) {       cout << -1 << endl;       return 0;     }     if (n < d + 1) {       cout << -1 << endl;       return 0;     }     for (int i = 0; i < h; ++i) {       cout << i + 1 <<     << i + 2 << endl;     }     if (d - h > 0) {       cout << 1 <<     << h + 2 << endl;     }     for (int i = 0; i < d - h - 1; ++i) {       cout << i + h + 2 <<     << i + h + 3 << endl;     }     for (int i = 0; i < n - d - 1; ++i) {       cout << h <<     << i + d + 2 << endl;     }     return 0;   }   