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

int main(void){
	int n;
	int *a;
	int flg = 1;
	scanf("%d", &n);
	a = (int *)malloc(sizeof(int) * n);
	for(int i=0; i<n; i++){
		scanf("%d", &a[i]);
	}
	qsort(a, n, sizeof(int), compare_int);
	for(int j=0; j<n-1; j++){
		if(a[j] == a[j+1]){
			flg = 0;
			break;
		}
	}
	if(flg == 1){
		printf("YES\n");
	} else if(flg == 0){
		printf("NO\n");
	}
	return 0;
}