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;

map <int, int> c;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, aux;
  cin >> n;
  bool ans = true;
  for (int i = 0; i < n; i++) {
    cin >> aux;
    if (c[aux] == 1) ans = false;
    else c[aux] = 1;
  }
  cout << (ans? "YES\n" : "NO\n");
  return 0;
}