#include <iostream>
#include<cstring>
#include<algorithm>
#include<vector>
#include<fstream>
using namespace std;
ifstream in("cmlsc.in");
ofstream out("cmlsc.out");
long int n, m, cnt;
long int a[1031], b[1031], rez[1031];
long int d[1031][1031];
int main()
{
    cin >> n >> m;
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < m; i++) cin >> b[i];
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            if (a[i - 1] == b[j - 1])d[i][j] = d[i - 1][j - 1] + 1;
            else d[i][j] = max(d[i - 1][j], d[i][j - 1]);
    for (int i = n; i >= 1;) {
        for (int j = m; j >= 1;)
            if (a[i - 1] == b[j - 1]) rez[cnt++] = a[i - 1], i--, j--;
            else if (d[i - 1][j] < d[i][j - 1]) j--;
            else i--;
    }cout << d[n][m] << '\n';
    for (int i = cnt - 1; i >= 0; i--) cout << rez[i] << " ";
}