public static long NextBiggerNumber(long n)
    {
      var numbersInN = NumbersIn(n);
        var pviotIndex = FindPivotIndex(numbersInN);
        if (pviotIndex == -1) return -1;

        var smallestNumberIndexAfterPivot = FindSmallestIndexAfterPivot(pviotIndex, numbersInN);
        Swap(numbersInN, pviotIndex, smallestNumberIndexAfterPivot);
        Sort(pviotIndex,numbersInN);
        return ConvertListToLong(numbersInN);
    }

        public static List<long> NumbersIn(long value)
    {
      if (value == 0) return new List<long>();
      var numbers = NumbersIn(value / 10);
      numbers.Add(value % 10);
      return numbers;
    }

    public static int FindPivotIndex(List<long> numbers)
    {
        for (var i = numbers.Count - 1; i > 0; i--)
        {
            if (numbers[i] > numbers[i-1]) return i-1;
        }
        return -1;
    }

    public static void Swap<T>(IList<T> list, int indexA, int indexB)
    {
        T tmp = list[indexA];
        list[indexA] = list[indexB];
        list[indexB] = tmp;
    }

    public static long ConvertListToLong(List<long> list)
    {
        long total = 0;
        foreach (long entry in list)
        {
            total = 10 * total + entry;
        }
        return total;
    }

    private static int FindSmallestIndexAfterPivot(int pivot, List<long> numbers)
    {
        var smallestNumberIndexAfterPivot = pivot + 1;
        for (var i = pivot + 1; i < numbers.Count; i++)
        {
            if (numbers[i] < numbers[smallestNumberIndexAfterPivot] && numbers[i] > numbers[pivot])
            {
                smallestNumberIndexAfterPivot = i;
            }
        }
        return smallestNumberIndexAfterPivot;
    }

    private static void Sort(int pviotIndex, List<long> numbers)
    {
        bool sorted = false;
        while (!sorted)
        {
            sorted = true;
            for (var i = pviotIndex + 1; i < numbers.Count; i++)
            {
                var compareIndex = i+1;
                if (compareIndex >= numbers.Count) break;
                if (numbers[i] > numbers[compareIndex])
                {
                    Swap(numbers, i, compareIndex);
                    sorted = false;
                }
            }
        }
    }