#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--;

sub[++x]=b[i];
i--;j--;
}
g<<a[n][m]<<"\n";
for (i=x;i>=1;i--)
    g<<sub[i]<<" ";

    return 0;
}