#include <stdio.h>

#define max(a,b) ((a>b) ? a : b)
#define NMax 1025

int M, N, A[NMax], B[NMax], D[NMax][NMax], sir[NMax], bst;

int main()
{
    int i,j;

    freopen("cmlsc.in", "r", stdin);
    //freopen("cmlsc.out", "w", stdout);

    scanf("%d %d", &M, &N);
    for (i=1; i<=M; i++)
        scanf("%d", &A[i]);
    for (i=1; i<=N; i++)
        scanf("%d", &B[i]);

    for (i=1; i<=M; i++)
        for (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]);

    bst = 0;
    for (i=M, j=N; i; )
        if (A[i] == B[j])
            sir[++bst] = A[i], --i, --j;
        else if (D[i-1][j] < D[i][j-1])
            --j;
        else
            --i;

    printf("%d\n",bst);
    for (i=bst; i; --i)
        printf("%d ", sir[i]);

    return 0;
}