Programing problem : Toph-Easyproblem-Pie Are Squared

Programing problem : Toph-Easyproblem-Pie Are Squared

Given the radius of a circle, calculate and print its area.

The area of a circle can be computed using the following formula:

$A = \pi r^2$

For pi, you can use 3.141592653589793, or acos(-1).

Input

The input will contain one floating point number r (r < 2000).

Output

Print the area of the circle (accurate to 10-4).

Solution : Code in  C  language 

#include<stdio.h> int main(){ int r; double pi=3.141592653589793,area; scanf("%d",&r); area=pi*r*r; printf("%f",area); return 0; }