#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int n, m, a[1040], b[1040], i, j, rez[1040], rezl, nr, c[1040][1040];
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])
                c[i][j] = c[i-1][j-1] + 1;
            else c[i][j] = max(c[i-1][j], c[i][j-1]);
        }
    i = n;
    j = m;
    while(i && j)
    {
        if(a[i] == b[j])
        {
            rezl++;
            rez[rezl] = a[i];
            i--;
            j--;
        }
        else
        {
            if(c[i-1][j] > c[i][j-1])
                 i--;
            else j--;
        }
    }
    fout << c[n][m] << '\n';
    for(i=rezl; i >= 1; i--)
        fout << rez[i] << ' ';
    return 0;
}