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 a[200000];
	int n;
	int flag = 0;
	int k, k1;

	scanf("%d", &n);
	for (k = 0; k < n; k++) {
		scanf("%d", &a[k]);
		for(k1 = 0; k1 < k; k1++){
			if (a[k1]==a[k]) { flag = 1; }
		}
	}

	if (flag == 0) {
		puts("YES");
	} else {
		puts("NO");
	}

	return 0;
}