func_code_string: #include <bits/stdc++.h>   using namespace std;   map<char, char> a;   int main() {     string s1, s2;     cin >> s1 >> s2;     int dl = s1.size();     int k = 0;     for (int i = 0; i < dl; i++) {       char p1 = s1[i];       char p2 = s2[i];       map<char, char>::iterator it = a.find(p1);       if (it == a.end()) {         a[p1] = p2;         if (p1 == p2) k++;       } else if (it->second != p2) {         cout << -1;         exit(0);       }       it = a.find(p2);       if (it == a.end()) {         a[p2] = p1;         if (p1 == p2) k++;       } else if (it->second != p1) {         cout << -1;         exit(0);       }     }     cout << (a.size() - k) / 2 <<   n ;     for (map<char, char>::iterator it = a.begin(); it != a.end(); it++) {       if (it->first >= it->second) continue;       cout << it->first <<     << it->second <<   n ;     }     return 0;   }   