#include<fstream>
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
int v[1030],k[1030],mat[1030][1030];
void refac(int i,int j);
int main()
{
    int i,j,l,r,s,m,n,p;
    in>>n>>m;
    for(i=1;i<=n;i++)
        in>>v[i];
    for(j=1;j<=m;j++)
        in>>k[j];
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
        {
            if(v[i]==k[j])
                mat[i][j]=1+mat[i-1][j-1];
            else
                mat[i][j]=max(mat[i-1][j],mat[i][j-1]);
        }
    out<<mat[n][m]<<"\n";
    refac(n,m);
}
 
void refac(int i,int j)
{
    if(i==0||j==0)return;
    if(v[i]==k[j])
    {
        refac(i-1,j-1);
        out<<v[i]<<" ";
        return;
    }
    if(mat[i-1][j]>mat[i][j-1])
        refac(i-1,j);
    else
        refac(i,j-1);
}