#include <iostream>
#include <fstream>
#define nmax 1030

using namespace std;

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

int n, m, a[nmax], b[nmax], d[nmax][nmax], s[nmax], k;

void read(){
    fin >> n >> m;
    for(int i = 0; i < n; ++i)
        fin >> a[i];
    for(int i = 0; i < m; ++i)
        fin >> b[i];
}

void solve(){
    for(int i = 0; i <= n; ++i)
        d[i][0] = d[0][i] = 0;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            if(a[i - 1] == b[j - 1])
                d[i][j] = d[i - 1][j - 1] + 1;
            else
                d[i][j] = max(d[i - 1][j], d[i][j - 1]);
}

void sol(){
    fout << d[n][m] << endl;
    for(int i = n; i >= 1; --i){
        for(int j = m; j >= 1; --j)
            if(d[i][j] == d[i - 1][j] && d[i][j] != d[i][j - 1]){
                i--;
            }
            else if(d[i][j] == d[i][j - 1] && d[i][j] != d[i - 1][j]){
                j--;
            }
            else if(d[i][j] == d[i][j - 1] && d[i][j] == d[i - 1][j]){
                j--;
            }
            else
                s[k++] = a[i - 1];
        }
    for(int i = k - 1; i >= 0; --i)
        fout << s[i] << " ";
}

int main()
{
    read();
    solve();
    sol();
    return 0;
}