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: Wrong Answer)

#include <stdlib.h>
#include <stdio.h>
int compare_int(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}
int main(void){
  int a=0;
  scanf("%d",&a);
  int b[a+1];
  int check = 0;
  for(int i=0; i<a; i++){
    scanf("%d",&b[i]);
  }
  qsort(b,a,sizeof(int),compare_int);
  for(int i=0; i<a; i++){
    if(b[i]==b[i+1]){
      check=1;
    }
  }
  if(check==1){
    printf("YES");
  }else{
    printf("NO");
  }
  }