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