#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  int a[n], b[m];
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i < m; i++) cin >> b[i];
  int mi = 10000;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (a[i] == b[j]) {
        mi = min(mi, a[i]);
      } else {
        mi = min(mi, a[i] * 10 + b[j]);
        mi = min(mi, b[j] * 10 + a[i]);
      }
    }
  }
  cout << mi << endl;
  return 0;
}
