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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
fscanf(STDIN, "%d", $n);
$inputs = array_map("intval", explode(" ", trim(fgets(STDIN))));
#$unique = array_unique($inputs, SORT_NUMERIC);
#$diff   = array_diff($inputs, $unique);
#var_dump([$n, $inputs]);
$ok = 1;
for ($i = 0; $n > $i; $i++) {
    $x = $inputs[$i];
    for ($j = $i + 1; $n > $j; $j++) {
        if ($x == $inputs[$j]) {
            $ok = 0;
            break 2;
        }
    }
}
echo $ok ? "Yes" : "No";