#include <bits/stdc++.h> using namespace std; int a[10001]; int main() { int n, k, sum = 0; cin >> n; for (int i = 1; i <= n; i++) { cin >> k; if (a[k] == 0) { a[k] = 1; sum++; } } cout << sum << endl; for (int j = 1; j <= 1000; j++) { if (a[j] != 0 ) { cout << j << ' ' ; } } return 0; }