#include <stdio.h>
#include <math.h>
int main ()
{
    double x1 , y1 , x2 , y2 , x3 , y3 ;
    scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
    double a , b , c  , p , s ;
    a = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
    b = sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
    c = sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
    p = a + b + c ;
	s = sqrt(p*(p-a)*(p-b)*(p-c));
	printf("%.2lf",s);
    return 0;
}