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

struct Point{
    int x,y;
    Point() : x(0),y(0) {}
    Point(int a,int b) : x(a),y(b) {}
    Point(long long a,long long b) : x(a),y(b) {}
    Point(double a,double b) : x(a),y(b) {}
    Point &operator=(const Point &b) = default;
    Point operator+(const Point &b){return Point(x+b.x,y+b.y);}
    Point operator-(const Point &b){return Point(x-b.x,y-b.y);}
    Point operator+=(const Point &b){return *this=*this+b;}
    Point operator-=(const Point &b){return *this=*this-b;}
    bool operator==(const Point &b){return x==b.x && y==b.y;}
    bool operator!=(const Point &b){return x!=b.x || y!=b.y;}
};

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N = 3;
    vector<Point> P(3);
    for(int i=0; i<N; i++){
        int x,y; cin >> x >> y;
        P.at(i) = {x,y};
    }

    vector<Point> dxy = {{-1,0},{0,1},{1,0},{0,-1}};
    int answer = 0;
    for(int i=0; i<4; i++) for(int k=0; k<4; k++) for(int l=0; l<4; l++){
        auto a = P.at(0);
        auto b = P.at(1);
        auto c = P.at(2);

        a += dxy.at(i); b += dxy.at(k); c += dxy.at(l);
        b -= a; c -= a;

        answer = max(answer,abs(b.x*c.y-b.y*c.x));
    }
    if(answer%2 == 0) cout << answer/2 << endl;
    else cout << answer/2 << ".5" << endl;
}