//王码1240

include <stdio.h>

include <math.h>

int main() {

double x1,y1,x2,y2,x3,y3,a,b,c,s,p;
scanf("%lf",&x1);
scanf("%lf",&y1);
scanf("%lf",&x2);
scanf("%lf",&y2);
scanf("%lf",&x3);
scanf("%lf",&y3);
a=sqrt(pow(x2-x1,2)+pow(y2-y1,2));
b=sqrt(pow(x3-x2,2)+pow(y3-y2,2));
c=sqrt(pow(x1-x3,2)+pow(y1-y3,2));
p=(a+b+c)/2;
s=sqrt(p*(p-a)*(p-b)*(p-c));
printf("%.2lf",s);
return 0;

}