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>

typedef const void cv;

int downint(cv *a, cv *b) {
  return *(int *)a < *(int *)b ? 1 : *(int *)a > *(int *)b ? -1 : 0;
}

int main(void){
  int n,a[200000],i,j;
  scanf("%d",&n);
  for(i=0;i<n;i++){
    scanf("%d",&a[i]);
  }
  
  qsort(a,n,sizeof(int),downint);
  for(i=0;i<n-1;i++){
      if(a[i] == a[i+1]){
      	printf("NO");
      	return 0;
      }
  }
  printf("YES");
  
  return 0;
}