Circle area

#include <stdio.h>
#define PI 3.14
int main(int argc, char argv[]){
	
	//计算圆面积
	float r = 0.0f;
	float area = 0.0f;

	scanf("%f", &r);

	area = PI*r*r;

	printf("圆的面积: %f\n",area);

	return 0;

}