using System;

class A

{ protected double a;

 protected double b;

 public A(double a, double b)

 {this.a=a;

  this.b=b;

 }

 public void Info()

 { Console.WriteLine(" a={0}  b={1}", a,b);

 }

 public double Sum()

 {return a+b;}

 public double Pr()

 {return a*b;}

}

​

class B:A

{ private double c;

public B(double a, double b, double c): base(a,b)

{this.c=c;

}

public void Info1()

 { Console.WriteLine(" a={0}  b={1} c={2}", a,b,c);

 }

 public double Sum1()

 {return a+b+c;}

 public double Pr1()

 {return a*b*c;}

}

public class Program

{

    public static void Main()

    {

        A a=new A(10,20);

        a.Info();

        Console.WriteLine("sum={0}    pr={1}", a.Sum(), a.Pr());

        B b=new B(10,20,30);

        b.Info1();

        Console.WriteLine("sum={0}    pr={1}", b.Sum1(), b.Pr1());

    }

}