#include <fstream>

using namespace std;

const int N = 1024;

int a[N+1], b[N+1], dp[N+1][N+1], m, n;

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

void refac_subsir(int l, int c)
{
    if(l == 0 || c == 0){
        return;
    }
    if(a[l] == b[c]){
        refac_subsir(l - 1, c - 1);
        out << a[l] << ' ';
    }
    else{
        if(dp[l-1][c] > dp[l][c-1]){
            refac_subsir(l - 1, c);
        }
        else{
            refac_subsir(l, c - 1);
        }
    }
}

int main()
{
    in >> m >> n;
    for(int i = 1; i <= m; i++){
        in >> a[i];
    }
    for(int j = 1; j <= n; j++){
        in >> b[j];
    }
    for(int i = 1; i <= m; i++){
        for(int j = 1; j <= n; j++){
            if(a[i] == b[j]){
                dp[i][j] = 1 + dp[i - 1][j - 1];
            }
            else{
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            }
        }
    }
    out << dp[m][n] << '\n';
    refac_subsir(m, n);
    in.close();
    out.close();
    return 0;
}