#include <iostream>
#include <vector>
#include <fstream>
#include <algorithm>
using namespace std;

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



int main(){
    int m, n;
    fin >> m >> n;
    vector<int> A(m), B(n);

    for(int i = 0; i < m; i++){
        fin >> A[i];
    }
    for(int i = 0; i < n; i++){
        fin >> B[i];
    }

    vector<vector<int>> dp(m+1, vector<int>(n+1, 0));

    for(int i = 1; i <= m; i++){
        for(int j = 1; j <= n; j++){
            if(A[i-1] == B[j-1]) dp[i][j] = dp[i-1][j-1] + 1;
            else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        }
    }

    vector<int> sol;

    int i = m, j = n;
    while(i > 0 && j > 0){
        if(A[i-1] == B[j-1]){
            sol.push_back(A[i-1]);
            i--, j--;
        }
        else {
            if(dp[i-1][j] > dp [i][j-1]) i--;
            else j--;
        }
    }

    reverse(sol.begin(), sol.end());

    fout << dp[m][n] << endl;

    for(auto c : sol){
        fout << c << " ";
    }
  
    return 0;
}