#include<bits/stdc++.h>
using namespace std;
double dis(double x1,double y1,double x2,double y2){
	double cnt=0;
	cnt=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
	return cnt;
}
int main(){
	double x3,y3,x1,y1,x2,y2,s=0,a=0,b=0,c=0,p=0;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	a=dis(x1,y1,x2,y2);
	b=dis(x1,y1,x3,y3);
	c=dis(x2,y2,x3,y3);
	p=(a+b+c)/2;
	s=sqrt(p*(p-a)*(p-b)*(p-c));//海伦公式 
	printf("%.2lf",s);
	return 0;
}