#include <bits/stdc++.h>
#define nmax 1030
using namespace std;

ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int n,m,a[nmax],b[nmax];
int lgmax[nmax][nmax];
int unde[nmax][nmax];
int i,j;

int main()
{
    fin>>n;fin>>m
    for(int i=1;i<=n;i++) fin>>a[i];
    for(int i=1;i<=m;i++) fin>>b[i];
    for(i=n;i>=0;i--)
        for(j=m;j>0;j--)
            if(a[i]==b[j])
    {
        lgmax[i][j]=1+lgmax[i+1][j+1];
        unde[i][j]=1;

    }
    else if(lgmax[i+1][j]>lgmax[i][j+1])
    {
        lgmax[i][j]=lgmax[i+1][j];
        unde[i][j]=2;
    }
    else
    {
        unde[i][j]=3;
        lgmax[i][j]=lgmax[i][j+1];

    }
    fout<<lgmax[1][1]<<'\n';
     i=1; j=1;
    while(i<=n && j<=m)
    {
        if(unde[i][j]==1)
        {
            fout<<a[i]<<" ";
        i++; j++;
        }
        else if (unde[i][j]==2) i++;
        else if(unde[i][j]==3)j++;
    }
    fout<<'\n';
    fout.close();
    return 0;
}