URI 1002 - Area of a Circle || Solution in C / C++

The formula to calculate the area of a circumference is defined as A = π . R2. Considering to this problem that π= 3.14159:

Calculate the area using the formula given in the problem description.

Input

The input contains a value of floating point (double precision), that is the variable R.

Output

Present the message "A=" followed by the value of the variable, as in the example bellow, with four places after the decimal point. Use all double precision variables. Like all the problems, don't forget to print the end of line after the result, otherwise you will receive "Presentation Error".

Input Samples	Output Samples
2.00	A=12.5664

100.64

A=31819.3103

150.00

A=70685.7750

SOURCE CODE

#include <stdio.h>

int main() {
  double a;
  scanf("%lf", & a);
  printf("A=%0.4lf\n", 3.14159 * a * a);
  return 0;
}