#include <iostream>
#include <fstream>
#define nmax 1024

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

int n, m, a[nmax], b[nmax], mx[nmax][nmax], c[nmax*2][2], k;

int main()
{
    ///Citire
    fin >> n >> m;

    for(int i=1; i<=n; i++){
        fin >> a[i];
    }
    for(int i=1; i<=m; i++){
        fin >> b[i];
    }

    ///Creare matrice
    for(int i=1; i<=n; i++){
        for(int j=1; j<=m; j++){
            if(a[i] == b[j]){
                mx[i][j] = mx[i-1][j-1] + 1;
                c[k][0] = i;
                c[k][1] = j;
                k++;
            }
            else if(a[i] != b[j]) mx[i][j] = max(mx[i][j-1], mx[i-1][j]);
        }
    }

    fout<<mx[n][m]<<"\n";

    int poz = 0;
    for(int i=0; i<k-1; i++){
        if(c[i][0] > c[i+1][0] || c[i][1] > c[i+1][1]){
            for(int j=i; j<k; j++){
                c[j][0] = c[j+1][0];
            }
            k--;
        }
    }

    for(int i=0; i<k; i++){
        fout<<a[c[i][0]]<<" ";
    }


    return 0;
}