func_code_string: #include <bits/stdc++.h>   using namespace std;   int main(void) {     map<string, string> m;     int q;     cin >> q;     int i;     string s1, s2;     while (q--) {       cin >> s1 >> s2;       if (m.count(s1) == 0)         m[s2] = s1;       else {         m[s2] = m[s1];         m.erase(s1);       }     }     cout << m.size() << endl;     map<string, string>::iterator it;     for (it = m.begin(); it != m.end(); it++)       cout << it->second <<     << it->first << endl;   }   