using System;

using System.Text;                  

public class Program

{

       public static string ConvertString(int number) 

        {

            StringBuilder convertedString = new StringBuilder();

            char[] digitsChar = 

            { 

                '0', '1', '2', '3', '4',

                '5', '6', '7', '8', '9',  

            };

            int digit;

            while (number > 10) 

            {

                digit = number % 10;

                number /= 10;

                convertedString.Insert(0, digitsChar[digit]);

            }

​

            convertedString.Insert(0, digitsChar[number]);

            return convertedString.ToString();

        }

        public static string ConvertOctal(int number) 

        {

            char[] octDigits =

            {

                '0', '1', '2', '3', '4', 

                '5', '6', '7', '8',

            };

            StringBuilder octalString = new StringBuilder();

            while (number > 8)

            {

                octalString.Insert(0, octDigits[number % 8]);

                number /= 8;

            }

​

            octalString.Insert(0, octDigits[number]);

            return octalString.ToString();

        }

​

        public static string ConvertHex(int number) 

        {

            StringBuilder octalString = new StringBuilder();

            char[] hexDigits = 

            { 

                '0', '1', '2', '3', '4', '5',

                '6', '7', '8', '9', 'A', 'B', 

                'C', 'D', 'E', 'F',

            };

            while (number > 16)

            {

                octalString.Insert(0, hexDigits[number % 16]);

                number /= 16;

            }

​

            octalString.Insert(0, hexDigits[number]);

            return octalString.ToString();

        }

​

        public static string ConvertPositiveRadix(int number, int radix)

        {

            return radix switch 

            {

                10 => ConvertString(number),

                8 => ConvertOctal(number),

                16 => ConvertHex(number)

            };

        }

        public static void ConvertNegativeRadix(int number, int radix)

        {

            number = number < 0 ? number * -1 : number;

            long number_res = 0xFFFFFFFE - number - 1;

            string invertion = (ConvertHex((int)number_res));

            Console.WriteLine(invertion);

        }

    public static void Main()

    {

        int number = -127;

        ConvertNegativeRadix(number, 16);

    }

}