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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define SZ(X) ((int)(X).size())
#define endl "\n";
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	// freopen("input.txt", "r", stdin);
	// freopen("output.txt", "w", stdout);
	int n,a;
	cin>>n;
	set<int> s;
	for (int i = 0; i < n; ++i)
		{
			cin>>a;
			s.insert(a);
		}	
    SZ(s)==n?cout<<"YES":cout<<"NO";
   return 0;
}