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 (Clang 3.8.0) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
int mycomp(const void* pt, const void* pt1);
int main()
{
	long int ar[200001] = { 0 };
	long int n;
	scanf("%ld", &n);
	for (int i = 1; i <= n; i++) {
		scanf("%ld", &ar[i]);
	}
	qsort(ar + 1, n, sizeof(long int), mycomp);
	for (int i = 1; i < n; i++) {
		if (ar[i] == ar[i + 1]) {
			printf("NO"); return 0;
		}
	}
	printf("YES");
	return 0;
}
int mycomp(const void* pt, const void* pt1)
{
	const long int* st = (const long int*)pt;
	const long int* st1 = (const long int*)pt1;
	return *st - *st1;
}