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 PHP (5.6.30) (judge verdict: Time Limit Exceeded)

<?php
fscanf(STDIN, "%d", $num_count);

$num_arr = array_map("intval", explode(" ", trim(fgets(STDIN))));

$max = max($num_arr);

$count = 0;

// for ($i = 0; $i < $max; ++$i) {
//     $temp = array_filter($num_arr, function ($num) use($i) {
//         return $num < $i;
//     });
    
//     if (count($temp) === ($num_count/2)) {
//         ++$count;
//     }
// }
$left = 0;
$right = $num_count-1;

foreach ($num_arr as $num) {
    $temp = array_filter($num_arr, function ($n) use($num) {
        return $n < $num;
    });
    
    if (count($temp) === ($num_count/2)) {
        $left = $num;
        $right = $num+1;
        $count++;
        break;
    }
}

if ($count == 0) {
    echo "0\n";
    return;
}

for ($i = $left; $i > 0; --$i) {
    $temp = array_filter($num_arr, function ($n) use($i) {
        return $n < $i;
    });

    if (count($temp) !== ($num_count/2)) {
        $left = $i+1;
        break;
    }
}

for ($i = $right; $i > $max; ++$i) {
    $temp = array_filter($num_arr, function ($n) use($i) {
        return $n < $i;
    });

    if (count($temp) !== ($num_count/2)) {
        $right = $i;
        break;
    }
}

echo $right-$left, "\n";