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: Time Limit Exceeded)

#include <stdio.h>

int main(void)
{
	int N;
	int i = 0, j, k;

	scanf("%d\n", &N);

	int A[N];
	for(i = 0; i < N; i++)
	{
		scanf("%d", &A[i]);
	}

	for(j = 0; j < N; j++)
	{
		for(k = 1; k < N-j; k++)
		{
			if(A[j] == A[j + k])
			{
				printf("NO");
				return 0;
			}
		}
	}
	printf("YES");
	return 0;
}