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>
#define rep(i, n) for (int i = 0; i < (int) (n); i++)
#define MOD 1000000007
typedef long long ll;

#include <stdlib.h>

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

int main(){
	int n;
	scanf("%d", &n);
	int a[n];
	rep(i, n) scanf("%d", &a[i]);
	qsort(a, n, sizeof(int), compare_int);
    rep(i, n - 1){
    	if(a[i] == a[i + 1]){
    		printf("NO");
    		return 0;
    	}
    }
	printf("YES");
	return 0;
}