import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class pre366
{
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
    public static void main(String args[])
    {
        FastReader obj = new FastReader();
        int n = obj.nextInt(),m = obj.nextInt(),arr1[] = new int[n],arr2[] = new int[m];
        for(int i=0;i<n;i++) arr1[i] = obj.nextInt();
        for(int i=0;i<m;i++) arr2[i] = obj.nextInt();
        Arrays.sort(arr1);
        Arrays.sort(arr2);
        if(arr1[0]==arr2[0])
            System.out.println(arr1[0]);
        else
        {
            System.out.println(Math.min(arr1[0],arr2[0])+""+Math.max(arr1[0],arr2[0]));
        }
    }
}
