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

int main()
{
    int n,a[200000],i,j;
    scanf("%d",&n);
    for (i = 0; i < n; i++)
    {
        scanf("%d",&a[i]);
    }
    qsort(a,n,sizeof(int),asc);

    for (i = 0; i < n - 1; i++)
    {
        if(a[i] == a[i + 1])break;
    }
    if(i == n - 1)printf("YES");
    else printf("NO");
}