int[] numbers = new int[] { 3, 5, 6, 15, 25, 30, 45, 47, 68, 82, 99 };
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < numbers.Length-1; i++)
            {
                int j = i + 1;
                if (i == 0 && numbers[i]>0)
                {
                    sb.Append("0-" + (numbers[i] - 1) + " ");
                }
                if (j == numbers.Length - 1 && numbers[j]<99)
                {
                    sb.Append($"{numbers[j] - 1} - 99 " );
                }
                if ((numbers[j] - numbers[i]) <= 1)
                {
                    continue;
                }
                sb.Append($"{numbers[i] + 1}-{numbers[j] - 1}  ");
            }