public int[] twoSum(int[] numbers, int target) {
        if (numbers == null) return null;

        int low = 0, high = numbers.length - 1;
        while (low < high) {
            if (numbers[low] + numbers[high] == target) return new int[] {low + 1, high + 1};
            else if (numbers[low] + numbers[high] > target) --high;
            else ++low;
        }
        return null;
    }