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: Wrong Answer)

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

int compar(const void *p1, const void *p2);

int main()
{
	int i,n;
	
	scanf("%d",&n);
	
	int a[n];
	
	for(i = 0;i < n;i++)
	{
		scanf("%d",&a[i]);
	}
	
	qsort(a,n,sizeof(int),compar);
	
	for(i = 0;i < n-1;i++)
	{
		if(a[i] == a[i+1])
			break;
	}
	
	printf("%s\n",i == n - 1?"Yes":"No");
	
	return 0;
}

int compar(const void *a, const void *b)
{
	return *(int*)a-*(int*)b;
}