让用户输入天数，并计算这个天数是几周零几天
Console.WriteLine("请输入天数.");
string strtianshu = Console.ReadLine();
int tianshu = Convert.ToInt32(strtianshu);
int zhou =tianshu/7;
int tian = tianshu % 7;
Console.WriteLine("{0}天是{1}周，零{2}天",strtianshu,zhou,tian);
Console.ReadKey();