#include <bits/stdc++.h>
#define nmax 1025

using namespace std;

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

int n,m,a[nmax],b[nmax],dp[nmax][nmax],sol[nmax],len;

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

    for(i = 1; i <= n; i++)
        for(j = 1; j <= m; j++)
            if(a[i] == b[j])
            {
                dp[i][j] = max(dp[i-1][j],dp[i][j-1]) + 1;
                sol[++len] = a[i];
            }
            else
                dp[i][j] = max(dp[i-1][j],dp[i][j-1]);

    fout << dp[n][m] << "\n";
    for(i = 1; i <= len; i++)
        fout << sol[i] << " ";

    fin.close();
    fout.close();
    return 0;
}