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: Time Limit Exceeded)

#include <stdio.h>

int main(void)
{
  int n;
  scanf("%d", &n);
  int i;
  long a[n];
  i = 0;
  while (i < n)
  {
    scanf("%ld", &a[i]);
    i++;
  }
  
  int k = 0;
  i = 0;
  while (i + 1 < n)
  {
    k = i + 1;
    while (k < n)
    {
      if (a[i] == a[k])
      {
        printf("NO");
        return 0;
      }
      k++;
    }
    i++;
  }
  printf("YES");
  return 0;
}