圆的面积

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		//S=PI*R*R
		Scanner in = new Scanner(System.in);
		java.text.DecimalFormat df=new java.text.DecimalFormat("#.0000000");
		int r = in.nextInt();
		double s = Math.PI  * r * r;
		System.out.println(df.format(s));
	}

}