#include <bits/stdc++.h>

using namespace std;
ifstream fin ("cmlsc.in");
ofstream fout ("cmlsc.out");
int x[1025], y[1025], dp[1025][1025];

int main()
{
    vector<int> ans;
    int n,m;
    fin >> m >> n;
    for (int i = 1; i <= m; i++)
        fin >> x[i];
    for (int i = 1; i <= n; i++)
        fin >> y[i];

    for (int i = 1; i <= m; i++)
        for (int j = 1; j <= n; j++) {
            if (x[i] == y[j])
                dp[i][j] = dp[i - 1][j - 1] + 1;
            else
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
    int i = m, j = n;
    while (i && j) {
        if (dp[i][j] > dp[i - 1][j] && dp[i][j] > dp[i][j - 1]) {
            ans.push_back(x[i]);
            i--;
            j--;
        }
        else if (dp[i - 1][j] > dp[i][j - 1])
            i--;
        else
            j--;
    }
    fout << dp[m][n] << endl;
    for (i = ans.size() - 1; i >= 0; i--)
        fout << ans.at(i) << ' ';
    return 0;
}