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