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>
 
long long int compare(const void *a, const void *b){
  return (*(long long int *)a)- (*(long long int *)b);
}
 
int main(){
  int n;
  scanf("%d",&n);
  long long int a[n];
  for(int i=0;i<n;i++){
    scanf("%lld",&a[i]);
  }
  qsort(a,n,sizeof(long long int),compare);
  
  for(int i=0;i<n-1;i++){
    if(a[i]==a[i+1]){
      printf("NO");
      return 0;
    }
  }
  
  printf("YES");
  return 0;
}