URI 1002 - Area of a Circle solution in C

Problem link: 1002 - Area of a Circle
Solution in c language:

#include <stdio.h>
 int main()
 {
     double A,R,r=3.14159;
     scanf("%lf",&R);
     A=r*R*R;
     printf("A=%.4lf\n",A);
     return 0;
 }