func_code_string: #include <bits/stdc++.h>   using namespace std;   inline long long read() {     long long x = 0, f = 1;     char c = getchar();     while (c <  0  || c >  9 ) {       if (c ==  - ) f = 0;       c = getchar();     }     while (c >=  0  && c <=  9 )       x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();     return f ? x : -x;   }   long long n, m, ans, s = 1, num;   bool exia[20][20], exib[20][20], s1[20][20], s2[20][20];   signed main() {     n = read(), m = read();     for (long long i = 1; i <= n; i++) {       long long x = read(), y = read();       exia[x][y] = exia[y][x] = 1;     }     for (long long i = 1; i <= m; i++) {       long long x = read(), y = read();       exib[x][y] = exib[y][x] = 1;     }     for (long long i = 1; i <= 9; i++) {       for (long long j = 1; j <= 9; j++) {         if (i == j) continue;         for (long long k = 1; k <= 9; k++) {           if (i == k || j == k) continue;           if (exia[i][j] && exib[i][k]) {             s1[i][j] = s2[i][k] = 1;             ans = i;             if (num && num != i) s = 0;             num = i;           }         }       }     }     if (s)       printf( %lld , ans);     else {       ans = 0;       for (long long i = 1; i <= 9; i++) {         for (long long j = 1; j <= 9; j++) {           if (i == j) continue;           if (s1[i][j] && s1[j][i]) {             ans = -1;             break;           }           if (s2[i][j] && s2[j][i]) {             ans = -1;             break;           }         }       }       printf( %lld , ans);     }     return 0;   }   