func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     pair<int, int> a[n], b[m];     for (int i = 0; i < n; i++) {       cin >> a[i].first >> a[i].second;     }     for (int i = 0; i < m; i++) {       cin >> b[i].first >> b[i].second;     }     set<int> s;     for (int i = 0; i < n; i++) {       int f = 0;       for (int j = 0; j < m; j++) {         if (((a[i].first == b[j].first) || (a[i].first == b[j].second)) &&             ((a[i].second == b[j].first) || (a[i].second == b[j].second))) {           continue;         } else if ((a[i].first == b[j].first) || (a[i].first == b[j].second)) {           f = 1;         }       }       int tr = 1;       if (f) {         s.insert(a[i].first);         tr = 0;       }       for (int j = 0; j < m; j++) {         if (((a[i].first == b[j].first) || (a[i].first == b[j].second)) &&             ((a[i].second == b[j].first) || (a[i].second == b[j].second))) {           continue;         } else if ((a[i].second == b[j].first) || (a[i].second == b[j].second)) {           f += 1;           break;         }       }       if (f > 1) {         cout <<  -1 n ;         exit(0);       }       if (f && tr) {         s.insert(a[i].second);       }     }     for (int j = 0; j < m; j++) {       int f = 0;       int tr = 1;       for (int i = 0; i < n; i++) {         if (((a[i].first == b[j].first) || (a[i].first == b[j].second)) &&             ((a[i].second == b[j].first) || (a[i].second == b[j].second))) {           continue;         } else if ((b[j].first == a[i].first) || (b[j].first == a[i].second)) {           f = 1;         }       }       if (f) {         s.insert(b[j].first);         tr = 0;       }       for (int i = 0; i < n; i++) {         if (((a[i].first == b[j].first) || (a[i].first == b[j].second)) &&             ((a[i].second == b[j].first) || (a[i].second == b[j].second))) {           continue;         } else if ((b[j].second == a[i].first) || (b[j].second == a[i].second)) {           f += 1;           break;         }       }       if (f > 1) {         cout <<  -1 n ;         exit(0);       }       if (f && tr) {         s.insert(b[j].second);       }     }     if (s.size() == 1) {       auto it = s.begin();       cout << (*it);     } else {       cout <<  0 ;     }     return 0;   }   