#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;

ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;
    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}




int main()
{

    int Q;
    Q = 1;
    //cin >> Q;   

    while (Q--) {
        double a, b, c, d, e, f;
        cin >> a >> b >> c >> d >> e >> f;
        double ans = 0;
        for (int i = 0; i < 4; i++) {
            for (int j = 0; j < 4; j++) {
                for (int k = 0; k < 4; k++) {
                    double x1 = a, y1 = b, x2 = c, y2 = d, x3 = e, y3 = f;
                    if (i == 0)x1++; if (i == 1)x1--; if (i == 2)y1++; if (i == 3)y1--;
                    if (j == 0)x2++; if (j == 1)x2--; if (j == 2)y2++; if (j == 3)y2--;
                    if (k == 0)x3++; if (k == 1)x3--; if (k == 2)y3++; if (k == 3)y3--;
                    x2 -= x1; x3 -= x1; y2 -= y1; y3 -= y1;
                    ans = max(ans, abs(y3*x2 - x3*y2)/2);
                    //cout << x1 << " " << y1 << " " << x2 << " " << y2 << " " << x3 << " " << y3 << " ";
                    //cout << ans << endl;


                }
            }
        }
        cout << ans;
    }
        return 0;
}