C# Just want 入门

1. 终于明白为什么以前的程序在结尾部分会经常出现 input any key to exit！

using System;

namespace ConsoleApplication1
{
    class Concat
    {
        static void Main()
        {
            Console.WriteLine("Hello,world");
            String s1, s2, result;
            s1 = Console.ReadLine();
            s2 = Console.ReadLine();
            result = s1 + s2;
            Console.WriteLine("{0} + {1} = {2}",s1,s2,result);
            Console.WriteLine("input anykey to exit!");
            s2 = Console.ReadLine();
        }
    }
}