public function getCombination($quantity, $reset = false)
    {
        if (null !== $this->combination && !$reset) {
            return $this->combination;
        }

        $this->combination = null;

        if (!empty($combinations = $this->buildCombinations($quantity))) {
            // Sort combinations: prefer closest, then greater, then lower, finally smaller
            usort($combinations, function (AssignmentCombination $a, AssignmentCombination $b) use ($quantity) {
                if ($a->diff == $b->diff) {
                    if ($a->size == $b->size) {
                        return 0;
                    }

                    return $a->size < $b->size ? -1 : 1;
                }

                if (0 <= $a->diff) {
                    return intval(0 > $b->diff ? -1 : $a->diff - $b->diff);
                }

                return intval(0 < $b->diff ? 1 : $b->diff - $a->diff);
            });

            $this->combination = reset($combinations);
        }

        return $this->combination;
    }