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>

int cmpnum(const void * n1, const void * n2)
{
	if(*(int *)n1 >*(int *)n2)
	{
		return -1;
	}
	else if(*(int *)n1 < *(int *)n2)
	{
		return 1;
	}
	else
	{
		return 0;
}
}

int main(void)
{
	int n,i;
	int a[200000]={0};
	int k;
	int score=0;
	
	scanf("%d",&n);
	
	for(i=0;i<n;i++){
		scanf("%d",&k);
		a[i]=k;
	}
	qsort(a, sizeof(a)/ sizeof(a[0]),sizeof(int),cmpnum);
	for(i=0;i<n-1;i++){
		if(a[i]==a[i+1])
			score++;
	}
	
	if(score>0)
		printf("NO");
	else
		printf("YES");
}