Finding Area of a Circle

Problem Statement
Write a C program which reads the radius of a circle and finds out the area of the circle.

#include<stdio.h>
#define pi 3.14
int main()
{
  float r,area;
  printf("enter the value of radius of the circle \n");
  scanf("%f",&r);
  area= pi*r*r;
  printf("the value of area is %f\n",area);
  return 0;
}