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

#define maxim(a, b) ((a > b) ? a : b)
#define FOR(i, a, b) for (int i = a; i <= b; ++i)
#define NMax 1024

int M, N, A[NMax], B[NMax], D[NMax][NMax], sir[NMax], bst;

int main() {
    int i, j;

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

    fin >> M >> N;
    FOR(i, 1, M)
        fin >> A[i];
    FOR(i, 1, N)
        fin >> B[i];

    FOR(i, 1, M) {
        FOR(j, 1, N) {
            if (A[i] == B[j])
                D[i][j] = 1 + D[i - 1][j - 1];
            else
                D[i][j] = maxim(D[i - 1][j], D[i][j - 1]);
        }
    }

    for (i = M, j = N; i;) {
        if (A[i] == B[j]) {
            sir[++bst] = A[i];
            --i;
            --j;
        } else if (D[i - 1][j] < D[i][j - 1]) {
            --j;
        } else {
            --i;
        }
    }

    fout << bst << '\n';
    for (i = bst; i; --i)
        fout << sir[i] << " ";

    fin.close();
    fout.close();

    return 0;
}