func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     map<string, string> mp;     set<string> s;     for (int i = 0; i < n; i++) {       string old, edg;       cin >> old >> edg;       mp[old] = edg;       s.insert(edg);     }     map<string, string>::iterator p;     p = mp.begin();     vector<pair<string, string>> a;     for (p; p != mp.end(); p++) {       if (s.count(p->first)) continue;       string cur;       cur = p->first;       while (mp.count(cur)) {         cur = mp[cur];       }       a.push_back(make_pair(p->first, cur));     }     cout << a.size() <<   n ;     for (int i = 0; i < a.size(); i++)       cout << a[i].first <<     << a[i].second <<   n ;   }   