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