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 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

long compare(const void *a, const void *b)
{
	return *(long*)a - *(long*)b;
}


int main(void)
{
	long nums[200000];
	int n, flg = 0;
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		scanf("%ld", &nums[i]);
	}
	qsort(nums, n, sizeof(long), compare);
	for (int i = 0; i < n - 1 ; i++) {
		if (nums[i] == nums[i + 1]) {
			flg++;
			break;
		}
	}
	if (flg) {
		printf("NO\n");
	}
	else {
		printf("YES\n");
	}
	return 0;
}