#include <bits/stdc++.h>
using namespace std;

int main(){
	double xa,xb,ya,yb,xc,yc;
	cin>>xa>>ya>>xb>>yb>>xc>>yc;
	double ca=sqrt((xa-xb)*(xa-xb)+(ya-yb)*(ya-yb))/1.00;
	double cb=sqrt((xb-xc)*(xb-xc)+(yb-yc)*(yb-yc))/1.00;
	double cc=sqrt((xc-xa)*(ca-xa)+(yc-ya)*(yc-ya))/1.00;
	double p=(ca+cb+cc)/2;
	double s=sqrt(p*(p-ca)*(p-cb)*(p-cc));
	cout<<fixed<<setprecision(2)<<s;
}