#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;

#ifdef INFOARENA
ifstream f("cmlsc.in");
#define cout g
#else
ifstream f("date.in");
#endif // INFOARENA

ofstream g("cmlsc.out");

#define nmax 1025
#define nr(i,j) ((i-1)*m+j)
#define take_x(k) ((k-1)/m+1)
#define take_y(k) ((k-1)%m+1)

int a[nmax],b[nmax],dp[nmax][nmax],p[nmax*nmax];
int i,j,n,m;

void afis(int z)
{
    if(p[z]) afis(p[z]);
    int x=take_x(z),y=take_y(z);
    if(x && y) if(a[x]==b[y]) cout<<a[x]<<' ';
}

int main()
{
    f>>n>>m;
    for(i=1;i<=n;++i) f>>a[i];
    for(i=1;i<=m;++i) f>>b[i];

    for(i=1;i<=n;++i)
        for(j=1;j<=m;++j)
        {
            if(a[i]==b[j])
            {dp[i][j]=1+dp[i-1][j-1];
            p[nr(i,j)]=nr(i-1,j-1);
            }
            if(dp[i][j]<dp[i-1][j])
            {
                dp[i][j]=dp[i-1][j];
                p[nr(i,j)]=nr(i-1,j);
            }
            if(dp[i][j]<dp[i][j-1])
            {
                dp[i][j]=dp[i][j-1];
                p[nr(i,j)]=nr(i,j-1);
            }
        }

    cout<<dp[n][m]<<'\n';
    afis(nr(n,m));
    return 0;
}