#include <fstream>
using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int a[1025][1025],b[1025],c[1025],sub[1025];
int main()
{ 
	int n,m,i,j,x=0;
	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;
}