#include <bits/stdc++.h>
using namespace std;

const int N = 1026;
int n, m, a[N], b[N];
int dp[2][N], from[2][N];
vector <int> cmlsc;

void init(int l, int y1, int y2) {
    for(int i = max(0, y1 - 1); i <= y2; ++i) {
        from[l][i] = i;
        dp[l][i] = 0;
    }
}
void rec(int x1, int y1, int x2, int y2) {
    if(y1 > y2)return;
    if(x1 == x2) {
        for(int j = y1; j <= y2; ++j)
            if(b[j] == a[x1]) {
                cmlsc.push_back(a[x1]);
                return;
            }
        return;
    }
    int mid = (x1 + x2) / 2;
    bool l = 0;
    init(0, y1 , y2);
    for(int k = x1; k <= mid; ++k) {
        l ^= 1;
        init(l, y1, y2);
        for(int j = y1; j <= y2; ++j) {
            if(a[k] == b[j]) {
                dp[l][j] = dp[l ^ 1][j - 1] + 1;
            } else {
                if(dp[l ^ 1][j] > dp[l][j - 1] || (j == y1))
                    dp[l][j] = dp[l ^ 1][j];
                else dp[l][j] = dp[l][j - 1];
            }
        }
    }
    for(int j = y1; j <= y2; ++j) from[l][j] = j;
    for(int k = mid + 1; k <= x2; ++k) {
        l ^= 1;
        init(l, y1, y2);
        for(int j = y1; j <= y2; ++j) {
            if(a[k] == b[j]) {
                dp[l][j] = dp[l ^ 1][j - 1] + 1, from[l][j] = from[l ^ 1][j - 1];
            } else {
                if(dp[l ^ 1][j] > dp[l][j - 1] || (j == y1))
                    dp[l][j] = dp[l ^ 1][j], from[l][j] = from[l ^ 1][j];
                else dp[l][j] = dp[l][j - 1], from[l][j] = from[l][j - 1];
            }
        }
    }
    int val = from[l][y2];

    rec(x1, y1, mid, val);
    rec(mid + 1, val + 1, x2, y2);

}
int main() {
    ifstream cin("cmlsc.in");
    ofstream cout("cmlsc.out");
    cin >> n >> m;
    for(int i = 1; i <= n; ++i)cin >> a[i];
    for(int i = 1; i <= m; ++i)cin >> b[i];
    rec(1, 1, n, m);
    cout << cmlsc.size() << '\n';
    for(auto it : cmlsc)cout << it << ' ';
}