import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class solution {
    public static void main(String[] args) {
        FastScanner sc = new FastScanner();
        int n = sc.nextInt() ;
        int m = sc.nextInt() ;
        int minM = Integer.MAX_VALUE ;
        int minN = Integer.MAX_VALUE ;
        for (int i=0 ; i<n ; i++){
            int curr = sc.nextInt() ;
            if ( curr < minN)
                minN = curr ;
        }
        for (int i=0 ; i<m ; i++){
            int curr = sc.nextInt() ;
            if (curr < minM)
                minM = curr ;
        }
        if (minM == minN)
            System.out.println(minM);
        else
            System.out.println(minN + "" + minM);




        }




    static final Random random=new Random();

    static void ruffleSort(int[] a) {
        int n=a.length;//shuffle, then sort
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n), temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


}
// FastScanner credits - SecondThread