#include <fstream>
#define maxim(a, b) ((a > b) ? a : b)
#define NMax 1024
using namespace std;
ifstream f("cmlsc.in"); ofstream g("cmlsc.out");
int M,N,A[NMax],B[NMax],D[NMax][NMax],sir[NMax],bst,i,j;
int main(void)
{
    int i, j;
    f>>M>>N;
    for(i=1;i<=M;i++)f>>A[i];
    for(i=1;i<=N;i++)f>>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]=maxim(D[i-1][j],D[i][j-1]);
    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;
    g<<bst<<'\n';
    for(i = bst; i; --i)
        g<<sir[i]<<' ';
	g.close(); return 0;
}