import java.io.*;
import java.util.Scanner;


public final class Main {

	public static void main(String[] args) throws IOException {
		int m,n;
		int[] a,b,rez;
		int[][] s;
		Scanner in = new Scanner(new FileReader("cmlsc.in"));
		FileWriter out = new FileWriter("cmlsc.out");
		m = in.nextInt();
		a = new int[m+1];
		n = in.nextInt();
		b = new int[n+1];
		s = new int[m+1][n+1];
		for(int i=1; i<=m; i++)
			a[i] = in.nextInt();
		for(int i=1; i<=n; i++)
			b[i] = in.nextInt();
		
		for(int i=1; i<=m; i++)
			for(int j=1; j<=n; j++)
				if(a[i]==b[j])
					s[i][j] = 1+s[i-1][j-1];
				else
					s[i][j] = (s[i-1][j]>s[i][j-1] ? s[i-1][j]:s[i][j-1]);
		
		int count=0;
		rez = new int[(m>n ? m:n)];
		for(int i=m,j=n; i*j>0 ;)
			if(a[i]==b[j])
			{
				rez[count++]=a[i];
				i--;
				j--;
			}
			else
				if(s[i-1][j] < s[i][j-1])
					j--;
				else
					i--;
		out.write(String.valueOf(count) + '\n');
		for(int i=count-1; i>=0; i--)
			out.write(String.valueOf(rez[i]) + ' ');
		
		in.close();
		out.close();
	}

}