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

int		main(void)
{
	int	N;
	int	A[200000];
	int	i;
	int	j;

	i = -1;
	scanf("%d", &N);
	while (++i < N)
		scanf("%d", &A[i]);
	qsort(A, N, sizeof(int), asc);
	i = -1;
	j = 0;
	while (j < N)
	{
		if (A[i] == A[j])
		{
			printf("NO\n");
			return (0);
		}
		i++;
		j++;
	}
	printf("YES\n");
	return (0);
}