import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

public class SearchForPrettyIntegers{
    public static void main(String[] args){
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        _870A_ solver = new _870A_();
        solver.solve(1,in,out);
        System.out.close();
    }

    static class _870A_{
        public void solve(int testNumber,InputReader in,OutputWriter out){
            int n=in.nextInt(), m=in.nextInt();
            boolean[] a = new boolean[10];
            boolean[] b = new boolean[10];
            while(n-->0) a[in.nextInt()] = true;
            while(m-->0) b[in.nextInt()] = true;
            int A = 10;
			int B = 10;
            for(int i = 1;i <= 9;++i){
                if(a[i]) A = Math.min(A,i);
                if(b[i]) B = Math.min(B,i);
                if(a[i]&b[i]){
                    System.out.print(i);
                    return;
                }
            }
            System.out.print(Math.min(A,B)*10+Math.max(A,B));
        }

    }

    static class InputReader{
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream){
            this.stream=stream;
        }

        public int read(){
            if(numChars == -1){
                throw new InputMismatchException();
            }
            if(curChar >= numChars){
                curChar=0;
                try{
                    numChars = stream.read(buf);
                }catch(IOException e){
                    throw new InputMismatchException();
                }
                if(numChars <= 0){
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int nextInt(){
            int c = read();
            while(isSpaceChar(c)){
                c = read();
            }
            int sgn = 1;
            if(c == '-'){
                sgn = -1;
                c = read();
            }
            int res = 0;
            do{
                if(c < '0'||c > '9'){
                    throw new InputMismatchException();
                }
                res*=10;
                res+=c-'0';
                c = read();
            }while(!isSpaceChar(c));
            return res*sgn;
        }

        public boolean isSpaceChar(int c){
            if(filter != null){
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c){
            return c == ' '||c == '\n'||c == '\r'||c == '\t'||c == -1;
        }

        public interface SpaceCharFilter{
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter{
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream){
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer){
            this.writer = new PrintWriter(writer);
        }

        public void close(){
            writer.close();
        }

        public void print(int i){
            writer.print(i);
        }

    }
}