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 scanner = new Scanner(System.in);
int num = scanner.nextInt();
System.out.printf("%.2f", 3.14 * (double) num * (double) num);
}
}