#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i;
  cin >> n >> m;
  int a[n], b[m];
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < m; i++) cin >> b[i];
  sort(a, a + n);
  sort(b, b + n);
  (a[0] == b[0] ? cout << a[0] : cout << a[0] << b[0]);
}
