/*
* This program calcuates area of a circle, taking input fot its radius.
* Copyright (C) 2006 Roshan Baladhanvi
*
* This program is a free software; you can redistribute it and/or modify it under the terms of GNU 
* General Public License Version 2, as published by the Free Software Foundation
*
* This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY; without 
* even the implied warranty of MECHANTIBILITY OR FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
* General Public License for more details. 
*
* The GPL License is currently published at the following URL 
* http://www.fsf.org/licensing/licenses/gpl.html
*
* The author of the program can be contacted at d_rosh2001 at yahoo dot co dot in
*/

#include<stdio.h>
#include<math.h>
#define PI 3.14159265

main(){
	float radius, area;
	
	printf("Enter radius of the circle: ");
		scanf("%f", &radius);
		
	if(radius <= 0){
		printf("Not a valid input. Quitting\n");
		exit(0);
	}
		
	area = PI * pow(radius, 2);
	
	printf("Area of circle with radius %.2f is %.2f\n", radius, area);
	
}