func_code_string: #include <bits/stdc++.h>   using namespace std;   map<string, string> mmap;   map<string, string>::iterator it;   int main() {     int t;     cin >> t;     while (t--) {       string a;       string b;       cin >> a >> b;       if (mmap[b] !=   ) {         for (it = mmap.begin(); it != mmap.end(); it++) {           if (it->first == b) {             mmap.erase(it);             break;           }         }       }       int flag = 0;       for (it = mmap.begin(); it != mmap.end(); it++) {         if (it->second == a) {           it->second = b;           flag = 1;           break;         }       }       if (!flag) mmap[a] = b;     }     int flag = 0;     for (it = mmap.begin(); it != mmap.end(); it++)       if (it->second ==   ) flag++;     cout << mmap.size() - flag << endl;     for (it = mmap.begin(); it != mmap.end(); it++)       if (it->second !=   ) cout << it->first <<     << it->second << endl;   }   