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