Problem:
Score : 100 points

Problem Statement

It is known that the area of a regular dodecagon inscribed in a circle of radius a is 3a^2.

Given an integer r, find the area of a regular dodecagon inscribed in a circle of radius r.

Constraints

1 \leq r \leq 100

r is an integer.

Input

Input is given from Standard Input in the following format:

r

Output

Print an integer representing the area of the regular dodecagon.

Sample Input 1

4

Sample Output 1

48

The area of the regular dodecagon is 3 \times 4^2 = 48.

Sample Input 2

15

Sample Output 2

675

Sample Input 3

80

Sample Output 3

19200

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

<?php
fscanf(STDIN, "%d", $n);
$a = array_map('intval', explode(' ', trim(fgets(STDIN))));
$b = []; $r = []; $m = 0;
for ($i=$n - 1; $i >= 0; $i--) {
    $b[$i] = (count_multiple($i + 1, $i + 1) % 2) === $a[$i] ? 0 : 1;
    if ($b[$i] === 1) {
        $r[] = $i + 1;
        $m++;
    }
}
echo $m."\n";
echo implode(' ', $r);
function count_multiple($i, $s) {
    global $b, $n;
    if ($i > $n - 1) return 0;
    return $b[$i] + count_multiple($i + $s, $s);
}
?>