function tapeEquilibrium(array $a): int
{
    $firstPart  = 0;
    $secondPart = array_sum($a);
    $min        = PHP_INT_MAX;
    for ($i = 0; $i < count($a) - 1; $i++) {
        $firstPart  += $i;
        $secondPart -= $i;
        $difference = abs($firstPart - $secondPart);
        $min        = $difference < $min ? $difference : $min;
    }

    return $min;
}