#include<bits/stdc++.h>
#define ll long long
#define f first
#define s second
#define N 1025
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
int a[N], b[N], dp[N][N], c[N];
int main(){
    int n,m,i,j;
    in>>n>>m;
    for(i=1; i<=n; ++i)
        in>>a[i];
    for(i=1; i<=m; ++i)
        in>>b[i];
    for(i=1; i<=n; ++i){
        for(j=1; j<=m; ++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]);
        }
    }
    out<<dp[n][m]<<"\n";
    i=0;
    while(dp[n][m]){
        if(a[n]==b[m])
            --n,--m, c[i++]=a[n+1];
        else{
            if(dp[n-1][m]>dp[n][m-1])
                --n;
            else --m;
        }
    }
    while(i--) out<<c[i]<<" ";
    return 0;
}