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 int_sort(const void *,const void *);
int main(void){
  
  int N,a[200001],i,j,w;
  scanf("%d",&N);
  for(i=0;i<N;i++){
    scanf("%d",&a[i]);
  }

  qsort(( void * )a , N , sizeof( int )
                       , int_sort );
 
  for(i=0;i<N-1;i++){
    if(a[i]==a[i+1]){
      printf("NO\n");
      return 0;
    }
  }
 printf("YES\n");
}



int_sort( const void * a , const void * b ) {
  /* 引数はvoid*型と規定されているのでint型にcastする */
  if( *( int * )a < *( int * )b ) {
    return -1;
  }
  else
  if( *( int * )a == *( int * )b ) {
    return 0;
  }
  return 1;
}