#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, count1 = 0, count2 = 0;
  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];
  }
  sort(a, a + n);
  sort(b, b + m);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (a[i] == b[j]) {
        count1++;
        cout << a[i] << endl;
        break;
      } else {
        continue;
      }
    }
    if (count1 > 0) {
      break;
    } else {
      continue;
    }
  }
  if (count1 == 0) {
    if (a[0] > b[0]) {
      cout << b[0] << a[0] << endl;
    } else {
      cout << a[0] << b[0] << endl;
    }
  }
  return 0;
}
