func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int tt;     cin >> tt;     unordered_map<string, string> mp;     unordered_set<string> s;     for (int i = 0; i < tt; i++) {       string s1;       string s2;       cin >> s1 >> s2;       if (s.find(s1) == s.end()) {         mp.insert({s1, s2});         s.insert(s2);       } else {         for (auto &it : mp) {           if (s1 == it.second) {             it.second = s2;             s.insert(s2);           }         }       }     }     cout << mp.size() << endl;     for (auto it : mp) {       cout << it.first <<     << it.second << endl;     }     return 0;   }   