static void Main(string[] args)
{
Calculator c = new Calculator();
int x = c.Add(2, 3);
string data = c.Today();
//Console.WriteLine(x); //有输入，有返回值
//Console.WriteLine(data); //无输入，有返回值
//c.PrintSum(4, 6); //有输入，无输出
c.PrintXTo0(20);
c.PrintXTo1(10);
int result = c.SumFrom1ToY(100);
Console.WriteLine(result);
Console.ReadLine();
}
static void Main(string[] args)
{
Calculator c = new Calculator();
int x = c.Add(2, 3);
Console.WriteLine(x);
string str = c.Today();
Console.WriteLine(str);
c.PrintSum(4, 6);
//====================
Calculator_b c2 = new Calculator_b();
c2.PrintXto1_a(10);
c2.PrintXto1_b(10);
}