#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  assert(1 <= n && n <= 200000);
  vector<bool> a(n);
  for (int i = 0; i < n; ++i) {
    int p;
    cin >> p;
    assert(0 <= p && p < n);
    assert(!a[p]);
    a[p] = 1;
  }
  for (bool&& i: a) assert(i);
}