计算

import java.util.Scanner;
public class abv {

/**
* @param args
*/
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
double pi=3.14;
double r=input.nextDouble();
double s=pi*r*r;
System.out.println("圆的面积是"+s);
// TODO Auto-generated method stub

}

}