func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<pair<string, string>>::iterator findit(       vector<pair<string, string>>::iterator st,       vector<pair<string, string>>::iterator en, string s) {     while (st != en) {       if ((*st).second == s) {         return st;       } else {         ++st;       }     }     return en;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     long long int q;     cin >> q;     string old, newi;     long long int i;     vector<pair<string, string>> v;     long long int count = 0;     for (i = 0; i < q; ++i) {       cin >> old >> newi;       vector<pair<string, string>>::iterator it = findit(v.begin(), v.end(), old);       if (it == v.end()) {         v.push_back(make_pair(old, newi));         count++;       } else {         (*it).second = newi;       }     }     cout << count <<   n ;     for (i = 0; i < count; ++i) {       cout << v[i].first <<     << v[i].second <<   n ;     }     return 0;   }   