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 <iostream>
#include<algorithm>
#include<sstream>
#include<cmath>
#include<vector>
#include<iomanip>
#include<map>
#include<set>
#include<queue>
#include<deque>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i,n) for(int i = 0; i < n;i++)
int main() {
	int n;cin >> n;vector<int> a(n);
	rep(i, n) cin >> a[i];
	sort(a.begin(), a.end());
	rep(i, n - 1) {
		if (a[i] == a[i + 1]) {
			cout << "NO" << endl;
			return 0;
		}
	}
	cout << "YES" << endl;
}