Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

int main()
{
  int n;
  bool ans = 1;
  cin >> n;
  vector<int> vec(n);
  for (int i = 0; i < n; i++)
    cin >> vec[i];
  sort(vec.begin(), vec.end());

  for (int i = 0; i < n - 1; i++)
  {
    if (vec[i] == vec[i + 1])
    {
      ans = 0;
      break;
    }
  }
  if (ans)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}