#include <fstream>

using namespace std;
ifstream f("cmlsc.in");
ofstream g("cmlsc.out");
int i,j,n,m,c[1035],b[1035],x=0,sub[1035],a[1025][1025];
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;
}