#include<cstdio>
#include<cmath>
double xa,ya,xb,yb,xc,yc;
double sq(double x){return x*x;}
double dist(double xa,double ya,double xb,double yb){
	return sqrt(sq(abs(xa-xb))+sq(abs(ya-yb)));
}
int main(){
    scanf("%lf%lf%lf%lf%lf%lf",&xa,&ya,&xb,&yb,&xc,&yc);
    int a=dist(xa,ya,xb,yb),b=dist(xa,ya,xc,yc),c=dist(xb,yb,xc,yc);
    double p=(a+b+c)/2;
    printf("%.2lf",sqrt(p*(p-a)*(p-b)*(p-c)));
    return 0;
}