#include <bits/stdc++.h>

using namespace std;

ifstream fin ("cmlsc.in");
ofstream fout ("cmlsc.out");

void usain_bolt()
{
    ios::sync_with_stdio(false);
    fin.tie(0);
}

const int N = 1025;

int a[N], b[N], dp[N][N], sol[N];

int main()
{
    int n, m;

    fin >> n >> m;
    for(int i = 1; i <= n; ++i) {
        fin >> a[i];
    }
    for(int i = 1; i <= m; ++i) {
        fin >> b[i];
    }
    for(int i = 1; i <= n; ++i) {
        for(int 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]);
            }
        }
    }
    int i = n, j = m;
    while(i >= 1 && j >= 1) {
        if(a[i] == b[j]) {
            sol[++sol[0]] = a[i];
            --i, --j;
        }
        else {
            if(dp[i - 1][j] >= dp[i][j - 1]) {
                --i;
            }
            else {
                --j;
            }
        }
    }
    fout << sol[0] << "\n";
    for(int i = sol[0]; i >= 1; --i) {
        fout << sol[i] << " ";
    }
    return 0;
}