func_code_string: #include <bits/stdc++.h>   using namespace std;   int q, w, e, W;   int a[500000], k, b, c, d, n, m, ip1, ip2, a1, b1, c1, d1, m1[500000],       m2[500000], m3[500000], m4[500000];   string old[2000], nov[2000], s1, s2;   int main() {     cin >> q;     for (int i = 1; i <= q; i++) {       cin >> s1 >> s2;       int ok = 0;       for (int j = 1; j <= k; j++)         if (nov[j] == s1) {           nov[j] = s2;           ok = 1;           break;         }       if (ok == 0) old[++k] = s1, nov[k] = s2;     }     cout << k << endl;     for (int j = 1; j <= k; j++) cout << old[j] <<     << nov[j] << endl;     return 0;   }   