#include <bits/stdc++.h>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int dp[1025][1025],v[1025],a[1025],b[1025],i,j,n,m,k;
int main()
{
    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] = dp[i-1][j-1]+1;
            else dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
    i=n,j=m;
    while(i && j)
    {
        if(a[i]==b[j])
        {
            v[++k]=a[i];
            i--;
            j--;
        }
        else if(dp[i-1][j] < dp[i][j-1]) j--;
        else i--;
    }
    fout<<k<<"\n";
    for(i=k; i>=1; --i) fout<<v[i]<<" ";
    return 0;
}