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

ifstream cin ("cmlsc.in");
ofstream cout ("cmlsc.out");

int a[1025],b[1025],dp[1025][1025],rez[1025];

int main(){
    int m,n;
    cin>>m>>n;
    for(int i=1;i<=m;i++)
        cin>>a[i];
    for (int i=1;i<=n;i++)
        cin>>b[i];
    for(int i=1;i<=m;i++){
        for(int j=1;j<=n;j++){
            if(a[i]==b[j])
                dp[i][j]=dp[i-1][j-1]+1;
            else
                dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        }
    }
    cout<<dp[m][n]<<"\n";
    int x=m,y=n,k=0;
    while(x>0 && y>0){
        if(a[x]==b[y]){
            rez[k++]=a[x];
            x--;
            y--;
        }
        else if(dp[x-1][y]>=dp[x][y-1])
            x--;
        else
            y--;
    }
    for(int i=k-1;i>=0;i--)
        cout<<rez[i]<<" ";
    return 0;
}