#include <stdio.h>
#include <bits/stdc++.h>

#define rep(i, n) for(int i = 0; i < (int)(n); i++)

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
const int INF = 0x3f3f3f3f;

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

int main(void) {
  // freopen("cmlsc.in", "r", stdin);
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(NULL);
  int N, M;
  fin >> M >> N;

  vi a(M), b(N);
  rep(i,M) { fin >> a[i]; }
  rep(i,N) { fin >> b[i]; }

  vector<vi> dp(M, vi(N));
  rep(i, M) { dp[i][0] = a[i] == b[0]; }
  rep(i, N) { dp[0][i] = a[0] == b[i]; }

  for (int i = 1; i < M; ++i)
  for (int j = 1; j < N; ++j) {
    if (a[i] == b[j]) {
      dp[i][j] = dp[i-1][j-1] + 1;
    } else {
      dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
    }
  }
  int ans = dp[M-1][N-1];
  fout << ans << "\n";
  vi res;
  int m = M-1, n = N-1;
  while(ans) {
    if (a[m] == b[n]) {
      res.push_back(a[m]);
      --ans;
      --m;
      --n;
    } else if (m > 0 && dp[m][n] == dp[m-1][n]) {
      --m;
    } else {
      --n;
    }

  }
  reverse(res.begin(), res.end());
  for(auto el: res) { fout << el << ' '; } fout << "\n";

  return 0;
}