DecToHex

using System;
using System.Collections.Generic;

/// <summary>
/// Using loops write a program that converts an integer number
/// to its hexadecimal representation. The input is entered as
/// long. The output should be a variable of type string. Do not
/// use the built-in .NET functionality.
/// </summary>
public class DecToHex
{
    public static void ConvertToHex(long input)
    {
        string output = string.Empty;
        long result = 0;
        List<string> inputHex = new List<string>();
        while (input >= 1)
        {
            result = input % 16;
            input /= 16;
            if (result < 10)
            {
                inputHex.Add(Convert.ToString(result));
            }
            else if (result == 10)
            {
                inputHex.Add("A");

            }
            else if (result == 11)
            {
                inputHex.Add("B");

            }
            else if (result == 12)
            {
                inputHex.Add("C");

            }
            else if (result == 13)
            {
                inputHex.Add("D");

            }
            else if (result == 14)
            {
                inputHex.Add("E");

            }
            else if (result == 15)
            {
                inputHex.Add("F");

            }
        }

        inputHex.Reverse();
        foreach (var num in inputHex)
        {
            output += num;
        }

        Console.WriteLine(output);
    }

    static void Main()
    {
        long input = long.Parse(Console.ReadLine());

        ConvertToHex(input);
    }
}