#include<bits/stdc++.h>
using namespace std;
int x,x2,x3,y,y2,y3,a,b,c;
double p,ans;
int main(){
    cin>>x>>y>>x2>>y2>>x3>>y3;
    a=sqrt((x-x2)*(x-x2)+(y-y2)*(y-y2));
    b=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
    c=sqrt((x3-x)*(x3-x)+(y3-y)*(y3-y));
    p=(a+b+c)/2;
    ans=sqrt(p*(p-a)*(p-b)*(p-c));
    cout<<fixed<<setprecision(2)<<ans;
	return 0;
}