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 (Clang 3.8.0) (judge verdict: Time Limit Exceeded)

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

int main(void)
{
	int n;
	int *a = NULL;
	int i, j;

	scanf("%d", &n);
	a = (int *)malloc(n * sizeof(int));

	for (i = 0; i < n; i++)
	{
		scanf("%d", a + i);
		for (j = i; j > 0; j--)
		{
			if (a[i] == a[j - 1])
			{
				goto NO;
			}
		}
	}

	if (0)
	{
	NO:
		printf("NO\n");
	}
	else
	{
		printf("YES\n");
	}
	return 0;
}