#include <iostream>
#include <fstream>
#include <cstring>
#define MAXX 3002
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int dp[MAXX][MAXX];
int s1[MAXX],s2[MAXX],rasp[MAXX];
int main()
{
    int l1,l2,i,j,k=1;
    fin>>l1>>l2;
    for(i=1;i<=l1;i++){
        fin>>s1[i];
    }
    for(i=1;i<=l2;i++){
        fin>>s2[i];
    }
    for(i=1;i<=l1;i++){
        for(j=1;j<=l2;j++){
            if(s1[i]==s2[j])
                dp[i][j]=dp[i-1][j-1]+1;
            else
                dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        }
    }
    i=l1;
    j=l2;
    while(i>=1 && j>=1){
        if(s1[i]==s2[j] && 1+dp[i-1][j-1]==dp[i][j]){
            rasp[k]=s1[i];
            k++;
            i--;
            j--;
        }
        else{
            if(dp[i-1][j]>dp[i][j-1]){
                i--;
            }
            else{
                j--;
            }
        }
    }
    i=1;
    j=k-1;
    while(i<=j){
        swap(rasp[i],rasp[j]);
        i++;
        j--;
    }
    fout<<k-1<<"\n";
    for(i=1;i<=k-1;i++){
        fout<<rasp[i]<<" ";
    }
}