taskK

#include<bits/stdc++.h>

#define endl "\n"
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;

constexpr int N = 1e5 + 5;

int n;
set<int> st;
vector<int> ans;

void Solve() {
  cin >> n;
  for (int i = 0, v; i < n; i++) {
    cin >> v;
    if (st.insert(v).second)
      ans.push_back(v);
  }
  cout << ans.size() << endl;
  for (int v: ans)
    cout << v << " ";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  // cin >> t;
  // while(t--)
  //auto start = chrono::high_resolution_clock::now();
    Solve();
  //auto end = chrono::high_resolution_clock::now();
  //cout << endl << (chrono::duration_cast<chrono::duration<double>>(end - start)).count();
  return 0;
}