#include<fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int b[1025],c[1025],n,m,a[1025][1025],x,sub[1025],i,j;
int main()
{
    f>>n>>m;
    for(i=1;i<=n;i++)
    f>>b[i];
    for(i=1;i<=m;i++)
    f>>c[i];
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    {
        if(b[i]==c[j])
        a[i][j]=a[i-1][j-1]+1;
        else
        a[i][j]=max(a[i-1][j],a[i][j-1]);
    }
    i=n;j=m;
    while(a[i][j])
    {
        while(a[i][j]==a[i-1][j])
        i--;
        while(a[i][j]==a[i][j-1])
        j--;
        x++;
        sub[x]=b[i];
        i--;
        j--;
    }
    g<<a[n][m]<<"\n";
    for(i=x;i>=1;i--)
    g<<sub[i]<<" ";
    return 0;
}