using System;

public class Circle

{

    public double xc;

    public double yc;

    public double r;

    public double XC;

    {

        set (xc=value)

        get {return xc}

    }

    public double yc

    {

        set (yc=value;)

        get (return yc;)

    }

    public double r

    {

        set (r=value;)

        get(return r;)  

    }

    public double S()

    {

        return Math.Pl*r*r;

    }

}

public class Program

{

    public static void Main()

    {

        Circle C1= new Circle();

        C1.xc=double.Parse(Console.ReadLine());

        C1.yc=double.Parse(Console.ReadLine());

        C1.r=double.Parse(Console.ReadLine());

        Console.WriteLine(C1.S());

    }

}