题解 | #牛牛的圆#
牛牛的圆
http://www.nowcoder.com/practice/75a202e826d048a39824ec694b5ce7e3
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int r=sc.nextInt();
System.out.printf("%.2f",3.14*r*r);
}
}
