#include <stdio.h>
#include <math.h>
double dist(double x1,double y1,double x2,double y2)
{return sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
}
int main()
{ double a,b,c,p,s,x[3],y[3];
int i;
for(i=0;i<3;i++)
scanf("%lf%lf",&x[i],&y[i]);
a=dist(x[0],y[0],x[1],y[1]);
b=dist(x[0],y[0],x[2],y[2]);
c=dist(x[1],y[1],x[2],y[2]);
p=(a+b+c)/2;
s=sqrt(p*(p-a)*(p-b)*(p-c));
printf("s=%f\n",s);
return 0;
}