#include <fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
#define nmax 1029
int N,A[nmax],B[nmax],D[nmax][nmax],M,sir[nmax],bst;
int main()
{
    f>>M>>N;
    for(int i=1; i<=M; i++)
        f>>A[i];
    for(int i=1; i<=N; i++)
        f>>B[i];
    for ( int i = 1 ; i<=M ; i++ )
        for ( int j = 1 ; j<=N ; j++ )
            if (A[i] == B[j])
                D[i][j] = 1 + D[i-1][j-1];
            else
                D[i][j] = max(D[i-1][j], D[i][j-1]);

    int i = M, j = N;
    while ( i>0 && j>0 )
        if (A[i] == B[j])
            sir[++bst] = A[i], --i, --j;
        else
        {
            if (D[i-1][j] < D[i][j-1])
                j--;
            else
                i--;
        }
    g<<bst<<endl;
    for ( int i = bst ; i>0 ; i-- ) g<<sir[i]<<" ";
    return 0;
}