这个咋写啊？啊…！😣

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class MyMath
{
static void Main(string[] args)
{
double pi = 3.14;
string num=Console.ReadLine();
double r = System.Convert.ToDouble(num);
Console.WriteLine("圆周长为:{0}",2 * pi * r);
Console.WriteLine("圆面积为:{0}",pi * r * r);
}
}
}