01.Gift Coverage

<?php
$side = floatval(readline());
$sheetCount = intval(readline());
$coverPerSheet = floatval(readline());

$presentArea = pow($side, 2) * 6;
$coverTotal = 0;
while ($sheetCount > 0) {
    if ($sheetCount % 3 == 0) {
        $coverTotal += $coverPerSheet * 0.25;
    } else {
        $coverTotal += $coverPerSheet;

    }
    $sheetCount--;
}
$percent = ($coverTotal / $presentArea) * 100;
printf("You can cover %.2f%% of the box.", $percent);