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