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: Runtime Error)

#include <stdio.h>
#include <string.h>

int main(void)
{
  int n, i, j, flag;
  int *a;
  scanf("%d", &n);
  i = 0;
  for (i = 0; i < n; i++)
  {
    scanf("%d", &a[i]);
  }
  flag = 0;
  for (i = 0; i < n; i++)
  {
    for (j = i + 1; j < n; j++)
    {
      if (a[i] == a[j])
      {
        flag = 1;
      }
    }
  }
  if (flag == 0)
  {
    printf("YES\n");
  }
  else
  {
    printf("NO\n");
  }
  return 0;
}