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

namespace CSharpRumenJD
{
    class Program
    {
        delegate void ProcessDelegate(int num);
        static void ShowDouble(int num)
        {
            num *= 2;
            Console.WriteLine(num);
        }
        static void ShowThree(int num)
        {
            num *= 3;
            Console.WriteLine(num);
        }
        static void ShowFour(int num)
        {
            num *= 4;
            Console.WriteLine(num);
        }
        /// <summary>
        /// 这里把委托作为参数传递给函数，
        /// </summary>
        /// <param name="pro"></param>
        /// <param name="num"></param>
        static void Excute(ProcessDelegate pro, int num)
        {
            pro(num);
        }
        static void Main(string[] args)
        {
            ProcessDelegate pro = null;
            string input = Console.ReadLine();
            if (input == "D")
                pro += ShowDouble; //关联函数的第一种方法
            else if (input == "F")
                pro = ShowFour; //关联函数的第二种方法
            else
                pro = new ProcessDelegate(ShowThree);//关联函数的第三种方法



            Excute(pro, 1);

            Console.ReadKey();
        }
    }
}