#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pi;
#define ALL(x) x.begin(),x.end()
#define rep(i,a,b) for(int i=a;i<b;i++)
using vi = vector<int>; 
using vvi = vector<vi>; 
using li =vector<ll>;
using lli=vector<li>;
using si =vector<char>;
using ssi =vector<si>;
const long long INF = 1e18;
const long long MOD=1e9+7;
//for (auto [key, val] : mp)
int main() { 
	int x1,x2,x3,y1,y2,y3;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;int ans=abs(x2*y3+x1*y2+x3*y1-x3*y2-x1*y3-x2*y1);
	rep(i,0,4)rep(j,0,4)rep(k,0,4){
		int X1=x1,X2=x2,X3=x3,Y1=y1,Y2=y2,Y3=y3;
		if(i==0)X1++;
		else if(i==1)X1--;
		else if(i==2)Y1++;
		else Y1--;
		if(j==0)X2++;
		else if(j==1)X2--;
		else if(j==2)Y2++;
		else Y2--;
		if(k==0)X3++;
		else if(k==1)X3--;
		else if(k==2)Y3++;
		else Y3--;
		ans=max(ans,abs(X2*Y3+X1*Y2+X3*Y1-X3*Y2-X1*Y3-X2*Y1));
		
	}
	double ANS=ans/(2.0);
	cout<<ANS;
}