func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, d, h;   vector<pair<int, int> > ans;   int main() {     ios::sync_with_stdio(0);     cin >> n >> d >> h;     if (2 * h < d || (d == 1 && n > 2)) {       cout << -1 <<   n ;       return 0;     }     for (int i = 2; i <= h + 1; i++) ans.push_back(make_pair(i - 1, i));     int idx = 1;     bool done = false;     for (int i = h + 2; i <= d + 1; i++) {       ans.push_back(make_pair(idx, i));       done = true;       idx = i;     }     if (done)       idx = 1;     else       idx = 2;     for (int i = d + 2; i <= n; i++) ans.push_back(make_pair(idx, i));     for (int i = 0; i < ans.size(); i++)       cout << ans[i].first <<     << ans[i].second <<   n ;     return 0;   }   