Diogenes Calc C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DiogenesCalc
{
    class Program
    {
        static void Main(string[] args)
        {
            Double a;
            Double b;
            int c = 0;
            string answer = null;

            Console.WriteLine("Diogenes' Influence Calculator 1.0");
            Console.WriteLine("Credit: Diogenes of Sinope (#57714) & DezNutz (#54689)");
        START:
            Console.WriteLine();
            Console.WriteLine();

            Console.WriteLine("Hello, please select a calculator option below:");
            Console.WriteLine("CD : Charity Donation Calculator");
            Console.WriteLine("P  : Propaganda Calculator");
            Console.WriteLine("cls  : Clears Console");
            Console.WriteLine("Exit : Exit Calculator");
            answer = Console.ReadLine();
            if (String.Equals(answer, "cd", StringComparison.OrdinalIgnoreCase))
            {
            cdstart:
                Console.WriteLine();
                Console.WriteLine("Charity Donation Calculator");
                Console.Write("Current Influence: ");
                a = Convert.ToDouble(Console.ReadLine());
                Console.Write("Target Influence: ");
                b = Convert.ToDouble(Console.ReadLine());
                if (a > b)
                {
                    Console.WriteLine("ERROR: The Target Influence is less than the Current Influence.");
                    Console.WriteLine("Please try again!");
                    Console.WriteLine("Press any key to continue....");
                    Console.ReadKey();
                    goto cdstart;
                }
                else
                {
                    while (a < b)
                    {
                        a = a + (a * .05);
                        c++;
                    }
                    Console.WriteLine("It will take " + c + " Charity Donation Cards to reach this goal.");
                    c = 0;
                    Console.WriteLine("Press any key to continue....");
                    Console.ReadKey();
                    goto START;
                }
            }
            else if (String.Equals(answer, "p", StringComparison.OrdinalIgnoreCase))
            {
            pstart:
                Console.WriteLine();
                Console.WriteLine("Propaganda Calculator");
                Console.Write("Current Influence: ");
                a = Convert.ToDouble(Console.ReadLine());
                Console.Write("Target Influence: ");
                b = Convert.ToDouble(Console.ReadLine());
                if (a < b)
                {
                    Console.WriteLine("ERROR: The Target Influence is greater than the Current Influence.");
                    Console.WriteLine("Please try again!");
                    Console.WriteLine("Press any key to continue....");
                    Console.ReadKey();
                    goto pstart;
                }
                else
                {
                    while (a > b)
                    {
                        a = a - (a * .05);
                        c++;
                    }
                    Console.WriteLine("It will take " + c + " Propaganda Cards to reach this goal.");
                    c = 0;
                    Console.WriteLine("Press any key to continue....");
                    Console.ReadKey();
                    goto START;
                }

            }
            else if (String.Equals(answer, "exit", StringComparison.OrdinalIgnoreCase))
            {
                Console.WriteLine("Thank You for using our calculator, giving us some credits wouldn't hurt, Bye!");
                Console.ReadKey();

            }
            else if (String.Equals(answer, "cls", StringComparison.OrdinalIgnoreCase))
            {
                Console.Clear();
                goto START;
            }

            else
            {
                Console.WriteLine("Sorry, you entered and invalid input.  Please try again!");
                goto START;


            }
        }
    }
}