using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        for(int i = 0; i <= 11; i++) 

        {

            int binNum = Convert.ToInt32(ConvertToBinary(i));

            int octNum = Convert.ToInt32(ConvertToOctal(i));

            Console.WriteLine("BINARY: " + i + " = " + binNum + " = " + ConvertFromBase(binNum, 2));

            Console.WriteLine("OCTAL: " + i + " = " + octNum + " = " + ConvertFromBase(octNum, 8));

            Console.WriteLine();

        }

        Console.WriteLine("HEXADECIMAL 2:" + ConvertFromBase("2", 16));

        Console.WriteLine("HEXADECIMAL A:" + ConvertFromBase("A", 16));

        Console.WriteLine("HEXADECIMAL F:" + ConvertFromBase("F", 16));

        Console.WriteLine("HEXADECIMAL 10:" + ConvertFromBase("10", 16));

        Console.WriteLine("HEXADECIMAL 20:" + ConvertFromBase("20", 16));

    }

    private static string ConvertToBinary(int num)

    {

        if (num == 0)

            return "0";

        int numBits = 0;

        StringBuilder binNum = new StringBuilder();

        while (num - Math.Pow(2, numBits) >= 0)

            numBits++;

        numBits--;

        while (numBits >= 0)

        {

            if (num - Math.Pow(2, numBits) >= 0)

            {

                binNum.Append("1");

                num = num - (int) Math.Pow(2, numBits);

            }

            else

            {

                binNum.Append("0");

            }

            numBits--;

        }

        return binNum.ToString();       

    }

    private static string ConvertToOctal(int num)

    {

        if (num == 0)

            return "0";

        int numDigits = 0;

        StringBuilder octNum = new StringBuilder();

        while(num - Math.Pow(8, numDigits) >= 0)

            numDigits++;

        while(numDigits > 0)

        {

            int digit = 0;

            if (num - Math.Pow(8, numDigits - 1) >= 0)

            {

                digit = 1;

                while (num - (Math.Pow(8, numDigits - 1) * digit) >= 0)

                    digit++;

                digit--;

                num -= (int) Math.Pow(8, numDigits - 1) * digit;

            }

            octNum.Append(digit);

            numDigits--;

        }

        return octNum.ToString();

    }

    private static int ConvertFromBase(int num, int numBase)

    {

        if (num < 10)

            return num;

        int decNum = 0;

        int powCount = 0;

        int modulizor = 10;

        int digit = 0;

        while (num / modulizor > 0)

        {

            digit = num % modulizor;

            decNum += digit * (int) Math.Pow(numBase, powCount);

            num /= 10;

            powCount++;

        }

        digit = num % modulizor;

        decNum += digit * (int) Math.Pow(numBase, powCount);

        return decNum;

    }

    //Works up to hexadecimal (base 16)

    private static string ConvertFromBase(string num, int numBase)

    {

        int result = 0;

        int powCount = 0;

        for (int i = num.Length - 1; i >= 0; i--)

        {

            int digit = 0;

            switch (num[i])

            {

                case 'F':

                    digit = 15;

                    break;

                case 'E':

                    digit = 14;

                    break;

                case 'D':

                    digit = 13;

                    break;

                case 'C':

                    digit = 12;

                    break;

                case 'B':

                    digit = 11;

                    break;

                case 'A':

                    digit = 10;

                    break;

                default:

                    digit = num[i] - '0';

                    break;

            }

            result += digit * (int) Math.Pow(numBase, powCount);

            powCount++;

        }

        return result.ToString();

    }

}