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 Perl (v5.18.2) (judge verdict: Time Limit Exceeded)

#!/usr/bin/perl

use strict;
use warnings;

my $n = <STDIN>;

my @a;
{
    my $in = <STDIN>;
    @a = split(" ", $in);
}
for (my $i=0; $i<$n; $i++)
{
    for (my $j=$i+1; $j<$n; $j++)
    {
        if ($a[$i]==$a[$j])
        {
            print "NO\n";
            exit;
        }
    }
}

print "YES\n";