#include <bits/stdc++.h>

using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");
int n, m, a[1030], b[1030], dp[1030][1030];
int st[1030], top;

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