using System;

public class Program

{

    delegate double ProcessDelegate(double param1, double param2);

    static double Multiply(double param1,double param2) => param1*param2;

    static double Add(double param1,double param2) => param1+param2;

    static double Subtract(double param1,double param2) => param2-param1;

    static double Divide(double param1,double param2) => param1/param2;

    public static void Main()

    {

        ProcessDelegate process;

        Console.WriteLine("Enter 2 numbers and seperate them with a semicolon(;)");

        string numbers = Console.ReadLine();

        int sColonpos = numbers.IndexOf(';');

        double param1 = Convert.ToDouble(numbers.Substring(0,sColonpos));

        double param2 = Convert.ToDouble(numbers.Substring(sColonpos+1,numbers.Length- sColonpos -1));

        Console.Write("Enter M to multiply, D to divide, A to add, or S to subtract the 2nd number from the 1st number:");

        char input = Convert.ToChar(Console.ReadLine());

        switch(input)

        {

                case'M':

                process = Multiply;

                Console.Write("Multiply: {0} X {1} = ",param1,param2);

                break;

            case 'D':

                process = Divide;

                Console.Write("Divide: {0} / {1} = ",param1,param2);

                break;

            case 'A':

                process = Add;

                Console.Write("Add: {0} + {1} = ",param1,param2);

                break;

            case 'S':

                process = Subtract;

                Console.Write("Subtract: {0} X {1} = ",param2,param1);

                break;

            default:

                process = Multiply;

                Console.Write("Invalid Selection, Multiply Assumed... {0} X {1} = ",param1,param2);

                break;

        }

        Console.WriteLine(process(param1,param2));

    }

}