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 PHP (5.6.30) (judge verdict: Wrong Answer)

<?php

fscanf(STDIN,"%d",$n);
fscanf(STDIN,"%d",$chars);

$array = explode(" ", $chars);
$arrayNum = [];
$isOK = true;

foreach($array As $key => $val){
  if (array_key_exists($val, $arrayNum)) {
    $array[$val] ++;
    $isOK = false;
    break;
  } else {
    $arrayNum += array($val => 1);
  }
}

if($isOK){
  $answer = "YES";
} else {
  $answer = "NO";
}

echo $answer.PHP_EOL;