#include <bits/stdc++.h>

using namespace std;

int main() {
  int n;
  cin >> n;
  unordered_set<int> hash;
  deque<int> res;

  while (n--) {
    int x;
    cin >> x;
    if (hash.find(x) == hash.end()) {
      res.push_back(x);
      hash.insert(x);
    }
  }
  cout << res.size() << '\n';
  while (!res.empty()) {
    cout << res.front() << " ";
    res.pop_front();
  }
  cout << '\n';
}