#include <bits/stdc++.h>
using namespace std;
ifstream fin("cmlsc.in");
ofstream fout("cmlsc.out");

int v[100001],w[100001];
int a[1001][1001];
stack<int> st;

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