import java.util.*;

public class Pizza {

	public static void main(String[] args) {
		double size;
		
		Scanner input = new Scanner(System.in);
		
		System.out.print("Diameter: ");
		size = input.nextDouble();
		
		System.out.println();
		
		System.out.println("A pizza of diameter " + size + " has " + area(size/2) + " square inches of pizza");
	}
	
	public static double area (double radius) {
		return Math.PI * Math.pow(radius, 2);
	}

}