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 <string.h>
#define lop(i, n) for(i=0; i<n; i++)

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

int main()
{
	int n, i;
	long int A[200000];
	
	scanf("%d", &n);
	
	lop(i, n){
		scanf("%ld", &A[i]);
	}
	
	qsort(A, n, sizeof(long int), compare_int);
	
	for(i=1; i<n; i++){
		if(A[i-1]==A[i])printf("NO");
	}
	
	printf("YES");
	
return 0;
}