using System;

abstract class realFunction

{public abstract double calculate(double x);

 public abstract double calculate2(double a);

}

class squareFunction : realFunction

{public override double calculate(double x)

{return x*x;}

public override double calculate2(double a)

{return a+a;}

}

public class Program

{

    public static void Main()

    {squareFunction s=new squareFunction();

     squareFunction sb=new squareFunction();

     Console.WriteLine(s.calculate(5));

     Console.WriteLine(sb.calculate2(5));

    }

}