#include <fstream>
#include <vector>
#define MAX 1025
using namespace std;
ifstream fin ("cmlsc.in");
ofstream fout ("cmlsc.out");
int a[MAX], b[MAX];
int dp[MAX][MAX];
int main() {
    int i,j,n,m;
    fin>>n>>m;
    for (i=1; i<=n; i++) {
        fin>>a[i];
    }
    for (j=1; j<=m; j++) {
        fin>>b[j];
    }
    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]);
            }
        }
    }
    fout<<dp[n][m]<<endl;
    vector<int> v;
    i=n;
    j=m;
    while (i>0 && j>0) {
        if (a[i]==b[j]) {
            v.push_back(a[i]);
            i--;
            j--;
        } else if (dp[i-1][j]>=dp[i][j-1]) {
            i--;
        } else {
            j--;
        }
    }
    for (i=v.size()-1; i>=0; i--) {
        fout<<v[i]<<" ";
    }
    fout<<endl;
    return 0;
}