func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int a, b, aa, bb;     cin >> a >> b >> aa >> bb;     if (aa <= bb) aa = bb + 1;     vector<pair<int, int> > ans;     if (aa > a) {       cout << 0;       return 0;     } else {       for (int i = bb; i <= b; i++)         for (int j = (aa > i + 1 ? aa : i + 1); j <= a; j++) {           ans.push_back(make_pair(j, i));         }     }     sort(ans.begin(), ans.end());     cout << ans.size() << endl;     for (int i = 0; i < ans.size(); i++)       cout << ans[i].first <<     << ans[i].second <<   n ;     return 0;   }   