2 3
1 2 1 3
1 2 1 3 2 3
 3 7
8 2 7 9 8 1
3 1 8 1 2 7 4 7 4 2 1 4 4 6
 1 10
3 9
3 2 3 4 5 3 5 7 8 6 2 5 7 8 2 4 1 7 5 1
 12 1
6 2 6 4 8 6 6 9 5 6 6 1 9 1 1 3 3 9 2 4 5 2 8 1
6 7
 2 3
1 2 7 8
1 3 2 4 7 9
 3 2
1 2 1 3 2 3
1 2 4 5
 3 8
8 9 8 5 9 2
8 4 8 3 2 6 4 2 4 3 3 7 3 6 1 6
 8 5
7 9 6 7 4 7 2 1 4 9 2 9 4 2 9 6
8 7 1 8 8 5 3 5 3 8
 4 4
1 2 1 3 6 7 6 8
1 4 1 5 6 1 6 9
 3 10
6 1 4 1 4 6
7 1 8 1 8 5 3 2 9 7 9 3 5 9 5 3 5 7 7 2
 3 3
1 2 1 3 2 3
1 2 1 3 2 3
 11 1
2 6 1 4 7 9 7 6 8 1 4 8 4 7 7 2 1 7 9 6 6 5
3 1
 5 6
1 7 5 6 6 9 3 6 1 9
2 7 2 5 8 5 4 8 4 2 8 2
 8 1
1 6 7 6 7 3 9 2 1 2 8 6 2 3 4 1
8 3
 9 4
2 8 8 9 8 1 9 2 5 9 3 5 3 2 5 2 9 1
8 4 8 7 6 8 4 7
 4 7
9 2 4 1 2 3 2 7
6 1 5 4 7 5 6 3 1 5 8 1 1 4
 3 3
1 2 5 6 7 8
2 3 4 5 8 9
 1 7
8 4
9 8 8 2 6 8 8 1 7 8 2 1 9 5
 2 2
1 2 2 3
2 3 3 4
 12 12
6 7 5 4 7 8 2 9 8 5 3 5 1 6 7 3 7 9 5 7 1 8 6 8
6 4 2 1 7 8 1 6 8 5 9 8 1 5 7 2 5 9 6 3 9 2 9 4
 9 1
3 4 3 2 3 7 3 5 9 4 1 9 6 4 5 2 7 6
8 3
 9 2
9 6 1 6 2 5 7 3 8 1 7 2 9 1 2 8 3 8
6 4 4 5
 3 9
9 7 9 2 7 2
9 8 1 9 3 9 6 3 8 6 4 6 1 3 5 4 5 3
 3 6
3 5 7 4 7 5
3 9 3 2 8 6 6 2 8 2 6 9
 2 1
1 2 1 3
1 2
 9 1
1 8 7 6 7 2 7 9 4 1 4 3 3 8 4 6 9 6
9 4
 2 2
1 2 2 4
1 2 1 3
 6 9
8 1 8 4 2 8 2 1 4 1 4 2
8 3 8 6 7 8 5 8 6 7 5 7 9 6 5 6 5 3
 12 2
3 1 8 2 6 9 2 6 5 4 4 3 4 1 4 2 6 3 9 7 9 4 3 2
7 1 4 1
 2 1
4 5 6 7
4 7
 4 3
1 2 4 5 6 7 8 9
1 2 8 9 3 1
 12 12
7 6 3 8 8 4 4 7 1 9 9 5 7 5 4 9 8 6 2 7 7 3 3 6
9 1 2 4 9 8 5 3 6 7 3 8 2 7 5 9 6 4 3 1 2 6 1 4
 12 5
9 2 6 7 7 8 3 4 8 4 7 1 2 1 7 3 7 2 5 6 3 8 1 5
3 7 7 5 7 4 5 8 4 6
 7 6
6 2 9 2 6 5 2 4 1 2 4 5 6 7
3 9 5 1 9 8 9 5 3 4 2 3
 6 4
2 7 3 2 8 3 1 5 7 4 3 5
2 6 9 8 8 6 6 9
 10 2
4 9 2 1 5 1 6 2 6 7 2 7 5 8 1 7 5 3 9 1
9 7 1 4
 4 4
1 2 2 3 1 3 4 5
1 3 3 2 1 2 4 6
 3 4
2 1 8 9 3 1
1 2 4 5 6 7 8 9
 1 12
6 8
8 4 8 2 5 8 9 8 8 3 8 7 8 1 1 3 1 9 4 3 7 3 5 7
 4 4
1 2 3 4 5 6 7 8
2 3 4 5 6 7 8 1
 3 10
1 5 7 1 2 1
9 5 5 6 3 5 4 7 8 3 9 6 8 4 9 8 4 6 3 4
 3 2
1 2 4 5 6 7
4 7 1 3
 5 6
4 7 7 3 4 3 9 4 3 9
7 5 7 8 1 7 7 2 6 2 1 2
 7 3
2 6 6 7 6 4 6 1 9 6 7 4 1 9
6 5 3 6 6 8
 2 7
2 7 2 5
7 1 9 7 8 9 4 9 8 1 3 9 3 8
 2 2
1 2 1 3
1 2 1 3
 2 11
6 1 3 6
1 7 1 2 1 5 1 4 5 3 3 2 9 8 4 2 7 5 4 9 2 9
 12 12
1 6 2 6 8 3 6 4 4 8 7 2 7 5 9 4 2 4 9 5 8 5 3 6
2 8 6 9 2 6 7 4 6 5 6 3 5 8 7 8 7 1 1 9 9 7 7 3
 4 12
2 8 3 1 2 1 9 4
9 5 5 3 1 6 3 7 7 1 8 5 6 5 4 6 1 9 1 4 2 5 9 8

-1 -1 3 6 -1 -1 0 0 -1 1 -1 1 0 -1 8 -1 0 8 0 -1 3 0 9 3 1 -1 0 8 -1 -1 1 -1 -1 -1 0 -1 -1 1 8 -1 0 -1 7 6 7 1 0 -1 -1
#include <bits/stdc++.h>
using namespace std;
long long ceildiv(long long one, long long two) {
  if (one % two == 0) {
    return one / two;
  } else {
    return one / two + 1;
  }
}
long long power(long long n, long long pow, long long m) {
  if (pow == 0) return 1;
  if (pow % 2 == 0) {
    long long x = power(n, pow / 2, m);
    return (x * x) % m;
  } else
    return (power(n, pow - 1, m) * n) % m;
}
long long gcd(long long a, long long b) {
  if (!b) return a;
  return gcd(b, a % b);
}
long long factorial(long long n, long long mod) {
  if (n > 1)
    return (n * factorial(n - 1, mod)) % mod;
  else
    return 1;
}
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
vector<long long> read(long long n) {
  vector<long long> a;
  for (long long i = 0; i < n; i++) {
    long long x;
    cin >> x;
    a.push_back(x);
  }
  return a;
}
vector<vector<long long>> adj;
void init(long long n) {
  for (long long i = 0; i <= n; i++) {
    vector<long long> a;
    adj.push_back(a);
  }
}
void solve() {
  long long n, m;
  cin >> n >> m;
  vector<long long> a = read(n * 2);
  vector<long long> b = read(m * 2);
  long long tot = 0;
  for (long long i = 0; i < 2 * n; i += 2) {
    long long f = 0, s = 0;
    for (long long j = 0; j < 2 * m; j += 2) {
      if (min(a[i], a[i + 1]) == min(b[j], b[j + 1]) &&
          max(a[i], a[i + 1]) == max(b[j], b[j + 1])) {
        continue;
      }
      if (b[j] == a[i] || b[j + 1] == a[i]) {
        f++;
      }
      if (b[j] == a[i + 1] || b[j + 1] == a[i + 1]) {
        s++;
      }
    }
    tot += f + s;
  }
  if (tot == 1) {
    cout << 1 << endl;
    return;
  }
  tot = 0;
  for (long long i = 0; i < 2 * m; i += 2) {
    long long f = 0, s = 0;
    for (long long j = 0; j < 2 * n; j += 2) {
      if (min(b[i], b[i + 1]) == min(a[j], a[j + 1]) &&
          max(b[i], b[i + 1]) == max(a[j], a[j + 1])) {
        continue;
      }
      if (a[j] == b[i] || a[j + 1] == b[i]) {
        f++;
      }
      if (a[j] == b[i + 1] || a[j + 1] == b[i + 1]) {
        s++;
      }
    }
    tot += s + f;
  }
  if (tot == 1) {
    cout << 1 << endl;
    return;
  }
  tot = 0;
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < m; j++) {
      for (long long k = 0; k < m; k++) {
        if (j == k) {
          continue;
        }
        if ((a[2 * i] == b[2 * j] || a[2 * i] == b[2 * j + 1]) &&
            (a[2 * i + 1] == b[2 * k] || a[2 * i + 1] == b[2 * k + 1]) &&
            a[2 * i] != b[2 * k] && a[2 * i] != b[2 * k + 1] &&
            a[2 * i + 1] != b[2 * j] && a[2 * i + 1] != b[2 * j + 1]) {
          tot++;
        }
      }
    }
  }
  for (long long i = 0; i < m; i++) {
    for (long long j = 0; j < n; j++) {
      for (long long k = 0; k < n; k++) {
        if (j == k) {
          continue;
        }
        if ((b[2 * i] == a[2 * j] || b[2 * i] == a[2 * j + 1]) &&
            (b[2 * i + 1] == a[2 * k] || b[2 * i + 1] == a[2 * k + 1]) &&
            b[2 * i] != a[2 * k] && b[2 * i] != a[2 * k + 1] &&
            b[2 * i + 1] != a[2 * j] && b[2 * i + 1] != a[2 * j + 1]) {
          tot++;
        }
      }
    }
  }
  if (tot > 0) {
    cout << -1 << endl;
    return;
  } else {
    cout << 0 << endl;
    return;
  }
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  ;
  long long t = 1;
  while (t--) {
    solve();
  }
}
