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<stdio.h>
#include<string.h>
#include<stdlib.h>
 
int part(int a[],int left,int right){
  int x;
  int i,j;
  int t;
 
  x = a[right];
 
  i = left;
  j = right - 1;
  while(i < j){
    while(a[i] < x) i++;
    while(i < j && a[j] > x) j--;
 
    t = a[i]; a[i] = a[j]; a[j] = t;
  }
 
  t = a[i]; a[i] = a[right]; a[right] = t;
 
  return i;
}
 
void quicksort(int a[],int left,int right){
  int v;
 
  if(left >= right) return;
 
  v = part(a,left,right);
 
  part(a,left,right);
  quicksort(a,left,v - 1);
  quicksort(a,v + 1,right);
}
 
int main(){
  int n,i;
  int a[200000];
  int flag = 0;
 
  scanf("%d", &n);
 
  for(i = 0;i < n;i++) scanf("%d", &a[i]);
 
  quicksort(a,0,n - 1);
 
  for(i = 0;i < n - 1;i++){
    if(a[i] == a[i + 1]){
      printf("NO\n");
      flag = 1;
      break;
    }
  }
 
  if(flag == 0) printf("YES\n");
 
  return 0;
}