#include <cstdio>   
#include <fstream>   
#include <algorithm>   
  
using namespace std;   
int v[1025][2];   
int dp[1025][1025];   
int main() {   
    ifstream fin("cmlsc.in");   
    ofstream fout("cmlsc.out");    
    int n, m;   
    fin >> n >> m;   
    int i, j, k;   
    for (i = 1; i <= n; ++i) fin >> v[i][0];   
    for (i = 1; i <= m; ++i) fin >> v[i][1];   
    for (i = 1; i <= n; ++i)    
    for (j = 1; j <= m; ++j) {   
        dp[i][j] = max(dp[i-1][j], dp[i][j-1]);   
        if (v[i][0] == v[j][1]) dp[i][j] = max(dp[i][j], dp[i-1][j-1] + 1);   
    }      
    fout << dp[n][m] << '\n';   
    k = 0;   
    int aux[1025];   
    while (n != 0 && m != 0) {   
        if (v[n][0] == v[m][1]) {n--; m--; aux[++k]=v[n+1][0];continue;}   
        if (dp[n-1][m] > dp[n][m-1]) {n--; continue;}   
        m--;   
    }   
    while (k--) {fout << aux[k+1] << ' ';}   
    fout << '\n';   
    return 0;   
}