#include <stdio.h>
#include<stdlib.h>

int n, m, c[1030][1030], a[1030], b[1030], sol[1000], nr, maxim;

int max(int x, int y)
{
    return x > y ? x : y;
}

int main(){
    FILE *fin, *fout;
    fin=fopen("cmlsc.in", "r");
    fout=fopen("cmlsc.out", "w");

    int i, j;
    fscanf(fin, "%d %d",&n,&m);
    for (i = 1; i <= n; i++)
        fscanf(fin,"%d",a + i);
    for (i = 1; i <= m; i++)
        fscanf("%d",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]);

    maxim = c[n][m];

    for (i = n; i >= 1; i--)
        for (j = m; j >= 1; j--)
            if (c[i][j] == maxim && (c[i][j-1] != maxim && c[i-1][j] != maxim)) sol[++nr] = a[i], maxim--;

    fprintf(fout, "%d\n",c[n][m]);
    for (i = nr; i >= 1; i--)
        fprintf(fout, "%d ",sol[i]);
    return 0;
}