Blue Bridge Cup--the area of the entrance training circle

Entry Training Circle Area time limit: 1.0s memory limit: 256.0MBThe problem describes the radius r of a given circle, and the area of the circle. Input format input contains an integer r that represents the radius of the circle. Output format output one row, containing a real number, rounded to retain 7 digits after the decimal point, indicating the area of the circle.

Description: In the subject, the input is an integer, but the output is a real number.

For the real output of the problem, please be sure to see the real output of the requirements, such as the need to retain the decimal point 7, your program must be strictly output 7 decimal places, output too much or too little number of decimal places are not, will be considered wrong.

The problem with the real output if not specifically stated, rounding is done by rounding.

Sample input 4 Sample output 50.2654825 data size and convention 1 <= R <= 10000. Please note that the value of π should be more accurate if the accuracy requirement is higher. You can use constants to denote π, such as pi=3.14159265358979323, or you can use mathematical formulas to find π, such as Pi=atan (1.0).

#include <iostream>#include<cstdio>#define pi 3.14159265358979323using  namespace  std; int Main () {  int  R;  scanf ("%d",&R);  printf ("%.7lf\n", pi*r*R);}

Blue Bridge Cup--the area of the entrance training circle