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>

sort(_num1, _num2)
const void* _num1;
const void* _num2;
{
	long long num1 = *(const long long*)_num1;
	long long num2 = *(const long long*)_num2;
	if (num1 < num2)
		return -1;
	if (num1 > num2)
		return 1;
	if (num1 == num2)
		return 0;
}

main(void) {
	unsigned N = 0;
	scanf("%u", &N);
	long long* llarray = malloc(sizeof(long long) * N);
	for (int i = 0; i < N; i++) {
		scanf("%lld", &llarray[i]);
	}
	qsort((void*)llarray, N, sizeof(long long), sort);
	for (int i = 0; i < N; i++) {
		if (llarray[i] == llarray[i + 1]) {
			printf("NO");
			return 0;
		}
	}
	printf("YES");
	return 0;
}