#include <bits/stdc++.h>   using namespace std;   int main() {     int n, d, h;     cin >> n >> d >> h;     if (h * 2 < d) {       cout << -1;       return 0;     }     if (d == 1) {       if (n >= 3) {         cout << -1;         return 0;       }       if (n == 2) {         cout << 1 <<     << 2;         return 0;       }     }     for (int i = 2; i <= h + 1; i++) {       cout << i <<     << i - 1 << endl;     }     int b = d - h;     if (b > 0) {       cout << 1 <<     << h + 2 << endl;       for (int i = h + 3; i <= d + 1; i++) {         cout << i <<     << i - 1 << endl;       }     }     int hd = 1;     if (b == 0) {       hd = 2;     }     for (int i = d + 2; i <= n; i++) {       cout << hd <<     << i << endl;     }     return 0;   }   