#include<bits/stdc++.h>
using namespace std;
double x[3],y[3],ans[4],p;
int main(){
	cin>>x[0]>>y[0]>>x[1]>>y[1]>>x[2]>>y[2];
	if(x[0]==x[1]){
		ans[0]=fabs(y[0]-y[1]);
	}
	else{
		if(y[0]==y[1]){
			ans[0]=fabs(x[0]-x[1]);
		}
		else{
			ans[0]=sqrt(pow(fabs(x[0]-x[1]),2)+pow(fabs(y[0]-y[1]),2));
		}
	}
	if(x[2]==x[1]){
		ans[2]=fabs(y[2]-y[1]);
	}
	else{
		if(y[2]==y[1]){
			ans[2]=fabs(x[2]-x[1]);
		}
		else{
			ans[2]=sqrt(pow(fabs(x[2]-x[1]),2)+pow(fabs(y[2]-y[1]),2));
		}
	}
	if(x[0]==x[2]){
		ans[1]=fabs(y[0]-y[2]);
	}
	else{
		if(y[0]==y[1]){
			ans[1]=fabs(x[0]-x[2]);
		}
		else{
			ans[1]=sqrt(pow(fabs(x[0]-x[2]),2)+pow(fabs(y[0]-y[2]),2));
		}
	}
	p=(ans[0]+ans[1]+ans[2])/2;
	ans[3]=sqrt(p*(p-ans[0])*(p-ans[1])*(p-ans[2]));
	printf("%.2lf",ans[3]);
	return 0;
}