#include<fstream>
#include<iostream>
using namespace std;
int max(int x,int y)
{
    if(x>y) return x;
    else return y;
}
    ifstream fin("cmlsc.in");
    ofstream fout("cmlsc.out");
int main()
{
    int a[1025],b[1025],n,m,i,j,c[1025][1025],v[1025],p=1;
    fin>>n>>m;
    for(i=1;i<=n;++i) fin>>a[i];
    for(j=1;j<=m;++j) fin>>b[j];
     
    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
            if( a[i] == b[j] )
                c[i][j]=c[i-1][j-1]+1;
            else
            c[i][j]=max(c[i][j-1],c[i-1][j]);
             
    fout<<c[n][m]<<endl;
   
    i=n; j=m;
    while( j!=0 && i!=0)
	{
        if(a[i] == b[j])
        {
            v[p]=a[i];
            i--;
			j--;
			p++;
        }
        else if( c[i-1][j]>c[i][j-1]) i--;
        else j--;
    }
    p--;
    for(i=p;i>=1;--i) fout<<v[i]<<" ";
    fout<<endl;
     
    return 0;
}