Problem:
Score : 300 points

Problem Statement

Takahashi made N problems for competitive programming.
The problems are numbered 1 to N, and the difficulty of Problem i is represented as an integer d_i (the higher, the harder).

He is dividing the problems into two categories by choosing an integer K, as follows:

A problem with difficulty K or higher will be for ARCs.

A problem with difficulty lower than K will be for ABCs.

How many choices of the integer K make the number of problems for ARCs and the number of problems for ABCs the same?

Problem Statement

2 \leq N \leq 10^5

N is an even number.

1 \leq d_i \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
d_1 d_2 ... d_N

Output

Print the number of choices of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 1

6
9 1 4 4 6 7

Sample Output 1

2

If we choose K=5 or 6, Problem 1, 5, and 6 will be for ARCs, Problem 2, 3, and 4 will be for ABCs, and the objective is achieved.
Thus, the answer is 2.

Sample Input 2

8
9 1 14 5 5 4 4 14

Sample Output 2

0

There may be no choice of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 3

14
99592 10342 29105 78532 83018 11639 92015 77204 30914 21912 34519 80835 100000 1

Sample Output 3

42685

Solution in PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
$N = (integer)trim(fgets(STDIN));
$d = array_map('intval', explode(" ", fgets(STDIN)));

$arc = 0;
$abc = 0;
$cnt = 0;
$wide = array_sum($d)/$N;
$n = 0;
$a = 0;

while (1){
    foreach ($d as $i){
        if ($i>=$wide){
            $arc ++;
        }else {
            $abc ++;
        }
    }
    if ($abc==$arc){
        $cnt ++;
        if ($n == 0){
            $wide ++;
        }else {
            if ($a == 0){
                $wide = array_sum($d)/$N;
            }
            $a ++;
            $wide --;
        }
    }elseif ($arc>$abc){
        $n ++;
        if ($n >= 2){
            break;
        }$wide ++;
    }else {
        $n ++;
        if ($n >= 2){
            break;
        }$wide --;
    }
    $abc = 0;
    $arc = 0;
}
print $cnt-1;