#include <fstream>
#include <queue>

using namespace std;

ifstream inf("cmlsc.in");
ofstream outf("cmlsc.out");

const int NMAX = 1024;

int v1[NMAX];
int v2[NMAX];
int dp[NMAX][NMAX];
int q[NMAX];
int qlen;

void DFS(int i, int j) {
    if(i == 0 || j == 0) {
        return;
    }
    if(dp[i - 1][j - 1] == dp[i][j] - 1) {
        q[qlen++] = v1[i];
        DFS(i - 1, j - 1);
    }
    else if(dp[i - 1][j] == dp[i][j]) {
        DFS(i - 1, j);
    }
    else if(dp[i][j - 1] == dp[i][j]) {
        DFS(i, j - 1);
    }
}

int main() {
    int n, m;
    inf >> n >> m;
    for(int i = 0; i < n; i++) {
        inf >> v1[i];
    }
    for(int i = 0; i < m; i++) {
        inf >> v2[i];
    }
    dp[0][0] = (v1[0] == v2[0]);
    for(int i = 1; i < n; i++) {
        dp[i][0] = max(dp[i - 1][0], (int)(v1[i] == v2[0]));
    }
    for(int i = 1; i < m; i++) {
        dp[0][i] = max(dp[0][i - 1], (int)(v1[0] == v2[i]));
    }
    for(int i = 1; i < n; i++) {
        for(int j = 1; j < m; j++) {
            if(v1[i] == v2[j]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
            }
            dp[i][j] = max(dp[i][j], max(dp[i - 1][j], dp[i][j - 1]));
        }
    }
    outf << dp[n - 1][m - 1] << '\n';
    DFS(n - 1, m - 1);
    while(qlen--) {
        outf << q[qlen] << ' ';
    }
    return 0;
}