#include<stdio.h>
#define N 1030
int a[N],b[N],d[N][N],n,m,best,v[N];
inline int max(int x,int y)
{
        if(x>y)
                return x;
        return y;
}
int main()
{
        freopen("cmlsc.in","r",stdin);
        freopen("cmlsc.out","w",stdout);
        scanf("%d%d",&n,&m);
        int i,j;
        for(i=1; i<=n; i++)
                scanf("%d",&a[i]);
        for(i=1; i<=m; i++)
                scanf("%d",&b[i]);
        for(i=1; i<=n; i++)
        {
                for(j=1; j<=m; j++)
                        if(a[i]==b[j])
                                d[i][j]=d[i-1][j-1]+1;
                        else
                                d[i][j]=max(d[i-1][j],d[i][j-1]);
        }
        for(i=n, j=m; i&&j; )
        {
                if(a[i]==b[j])
                {
                        v[++best]=a[i];
                        i--;
                        j--;
                }
                else
                if(d[i-1][j]<d[i][j-1])
                        j--;
                else
                        i--;
       }
       printf("%d\n",best);
       for(i=best; i>0; i--)
                printf("%d ",v[i]);
       printf("\n");
       return 0;
}