/*   @JUDGE_ID:   1705PZ   438   C */
#include <stdio.h>
#include <math.h>

void swap(float *x,float *y){
float temp;
temp = *x;
*x = *y;
*y = temp;
}

int main(){
float x1,x2,x3,y1,y2,y3;
float x,y,r;
while(scanf("%f %f %f %f %f %f",&x1,&y1,&x2,&y2,&x3,&y3) == 6){
	if(y1 == y2){
		swap(&x2,&x3);
		swap(&y2,&y3);
		}
	else if(y2 == y3){
		swap(&x2,&x1);
		swap(&y2,&y1);
		}
	x = ((((y1 + y2) / 2) + ((x2 - x1) / (y2 - y1)) * ((x1 + x2) / 2))
  	   - (((y2 + y3) / 2) + ((x3 - x2) / (y3 - y2)) * ((x2 + x3) / 2)))
  	   / (((x2 - x1) / (y2 - y1)) - ((x3 - x2) / (y3 - y2)));
	y = -((x2 - x1) / (y2 - y1)) * x + (((y1 + y2) / 2) + ((x2 - x1)
  	   / (y2 - y1)) * ((x1 + x2) / 2));
	r = pow(((x - x1) * (x - x1) + (y - y1) * (y - y1)),0.5);
	printf("%.2f\n",2 * r * 3.141592653589793);
	}
return 0;
}
@END_OF_SOURCE_CODE