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

const string file_name = "cmlsc";
ifstream fin(file_name + ".in");
ofstream fout(file_name + ".out");

int n, m, v[1030], v2[1030], mat[1040][1040];

int main()
{
    fin >> n >> m;
    for(int i = 1; i <= n; i++)
        fin >> v[i];

    for(int i = 1; i <= m; i++){
        fin >> v2[i];
    }

    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            if(v[i] == v2[j])
                mat[i][j] = 1 + mat[i-1][j-1];
            else
                mat[i][j] = max(mat[i-1][j], mat[i][j-1]);
        }
    }

    int k = 1;

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

    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){

            if(mat[i][j] == k && v[i] == v2[j]){
                fout << v[i] << " ";
                k++;
            }
            else if(k > mat[n][m])
                return 0;

        }

    }

    return 0;
}