#line 2 "/Users/noya2/Desktop/Noya2_library/template/template.hpp"
using namespace std;

#include<bits/stdc++.h>
#line 1 "/Users/noya2/Desktop/Noya2_library/template/inout_old.hpp"
namespace noya2 {

template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p){
    os << p.first << " " << p.second;
    return os;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p){
    is >> p.first >> p.second;
    return is;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v){
    int s = (int)v.size();
    for (int i = 0; i < s; i++) os << (i ? " " : "") << v[i];
    return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &v){
    for (auto &x : v) is >> x;
    return is;
}

void in() {}
template <typename T, class... U>
void in(T &t, U &...u){
    cin >> t;
    in(u...);
}

void out() { cout << "\n"; }
template <typename T, class... U, char sep = ' '>
void out(const T &t, const U &...u){
    cout << t;
    if (sizeof...(u)) cout << sep;
    out(u...);
}

template<typename T>
void out(const vector<vector<T>> &vv){
    int s = (int)vv.size();
    for (int i = 0; i < s; i++) out(vv[i]);
}

struct IoSetup {
    IoSetup(){
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(15);
        cerr << fixed << setprecision(7);
    }
} iosetup_noya2;

} // namespace noya2
#line 1 "/Users/noya2/Desktop/Noya2_library/template/const.hpp"
namespace noya2{

const int iinf = 1'000'000'007;
const long long linf = 2'000'000'000'000'000'000LL;
const long long mod998 =  998244353;
const long long mod107 = 1000000007;
const long double pi = 3.14159265358979323;
const vector<int> dx = {0,1,0,-1,1,1,-1,-1};
const vector<int> dy = {1,0,-1,0,1,-1,-1,1};
const string ALP = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const string alp = "abcdefghijklmnopqrstuvwxyz";
const string NUM = "0123456789";

void yes(){ cout << "Yes\n"; }
void no(){ cout << "No\n"; }
void YES(){ cout << "YES\n"; }
void NO(){ cout << "NO\n"; }
void yn(bool t){ t ? yes() : no(); }
void YN(bool t){ t ? YES() : NO(); }

} // namespace noya2
#line 1 "/Users/noya2/Desktop/Noya2_library/template/utils.hpp"
namespace noya2{

unsigned long long inner_binary_gcd(unsigned long long a, unsigned long long b){
    if (a == 0 || b == 0) return a + b;
    int n = __builtin_ctzll(a); a >>= n;
    int m = __builtin_ctzll(b); b >>= m;
    while (a != b) {
        int mm = __builtin_ctzll(a - b);
        bool f = a > b;
        unsigned long long c = f ? a : b;
        b = f ? b : a;
        a = (c - b) >> mm;
    }
    return a << min(n, m);
}

template<typename T> T gcd_fast(T a, T b){ return static_cast<T>(inner_binary_gcd(abs(a),abs(b))); }

long long sqrt_fast(long long n) {
    if (n <= 0) return 0;
    long long x = sqrt(n);
    while ((x + 1) * (x + 1) <= n) x++;
    while (x * x > n) x--;
    return x;
}

template<typename T> T floor_div(const T n, const T d) {
    assert(d != 0);
    return n / d - static_cast<T>((n ^ d) < 0 && n % d != 0);
}

template<typename T> T ceil_div(const T n, const T d) {
    assert(d != 0);
    return n / d + static_cast<T>((n ^ d) >= 0 && n % d != 0);
}

template<typename T> void uniq(vector<T> &v){
    sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
}

template <typename T, typename U> inline bool chmin(T &x, U y) { return (y < x) ? (x = y, true) : false; }

template <typename T, typename U> inline bool chmax(T &x, U y) { return (x < y) ? (x = y, true) : false; }

template<typename T> inline bool range(T l, T x, T r){ return l <= x && x < r; }

} // namespace noya2
#line 8 "/Users/noya2/Desktop/Noya2_library/template/template.hpp"

#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define repp(i,m,n) for (int i = (m); i < (int)(n); i++)
#define reb(i,n) for (int i = (int)(n-1); i >= 0; i--)
#define all(v) (v).begin(),(v).end()

using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using pil = pair<int,ll>;
using pli = pair<ll,int>;

namespace noya2{

/*　~ (. _________ . /)　*/

}

using namespace noya2;


#line 2 "c.cpp"

template<class Rat>
requires std::constructible_from<Rat, int> && std::totally_ordered<Rat>
constexpr int sign(const Rat &x){
	const Rat Rat0 = Rat(0);
	return (x < Rat0 ? -1 : x > Rat0 ? 1 : 0);
}

template<class Rat>
struct point {
    Rat x, y;
    point () {}
    point (Rat _x, Rat _y) : x(_x), y(_y) {}
    point &operator+=(const point &r){
        x += r.x;
        y += r.y;
        return *this;
    }
    point &operator-=(const point &r){
        x -= r.x;
        y -= r.y;
        return *this;
    }
    point operator+() const {
        return *this;
    }
    point operator-() const {
        x = -x;
        y = -y;
        return *this;
    }
    point &operator*=(const Rat &a){
        x *= a;
        y *= a;
        return *this;
    }
	point &operator/=(const Rat &a){
        x /= a;
        y /= a;
        return *this;
    }
    friend point operator+(const point& lhs, const point& rhs){
        return point(lhs) += rhs;
    }
    friend point operator-(const point& lhs, const point& rhs){
        return point(lhs) -= rhs;
    }
    friend point operator*(const point& lhs, const Rat& a){
        return point(lhs) *= a;
    }
    friend point operator*(const Rat& a, const point& rhs){
        return point(rhs) *= a;
    }
	friend point operator/(const point& lhs, const Rat& a){
        return point(lhs) /= a;
    }
    auto operator<=>(const point&) const = default;
    friend std::ostream &operator<<(std::ostream &os, const point& p){
        return os << p.x << ' ' << p.y;
    }
    friend std::istream &operator>>(std::istream &is, point &a){
        Rat _x, _y; is >> _x >> _y;
        a = point(_x, _y);
        return (is);
    }
    friend Rat norm(const point &a) {
        return a.x*a.x + a.y*a.y;
    }
    friend Rat dot(const point &a, const point &b){
        return a.x*b.x + a.y*b.y;
    }
    friend Rat cross(const point &a, const point &b){
        return a.x*b.y - a.y*b.x;
    }
    int quadrant_atan2() const {
        // not origin point
        // ceil ( atan2(y,x) / (pi/2) )
		int signx = sign(x);
		int signy = sign(y);
		if (signx <= 0 && signy <  0) return -1;
		if (signx >  0 && signy <= 0) return  0;
		if (signx >= 0 && signy >  0) return  1;
		if (signx <  0 && signy >= 0) return  2;
        // origin point x == 0 && y == 0
        return 0;
    }
	friend int ccw(const point &a, point b, point c){
		b -= a;
		c -= a;
		int signcr = sign(cross(b, c));
		if (signcr > 0){
			// ccw       
			//           c
			// a --> b 
			return 1;
		}
		if (signcr < 0){
			// cw
			// a --> b
			//           c
			return -1;
		}
		if (sign(dot(b, c)) < 0){
			// c  a --> b
			return 2;
		}
		if (norm(b) < norm(c)){
			// a --> b   c
			return -2;
		}
		// a - b -> c
		return 0;
	}
	friend point rot90(const point &a){
		return point(-a.y, a.x);
	}
};

using vecl = point<int>;

void solve(){
    array<vecl,3> a;
    rep(i,3) in(a[i]);
    int ans = 0;
    auto mv = [&](vecl v, int dir){
        if (dir < 2){
            v.x += (dir % 2 ? 1 : -1);
        }
        else {
            v.y += (dir % 2 ? 1 : -1);
        }
        return v;
    };
    rep(i,4) rep(j,4) rep(k,4){
        auto vi = mv(a[0],i);
        auto vj = mv(a[1],j);
        auto vk = mv(a[2],k);
        chmax(ans,abs(cross(vj - vi, vk - vi)));
    }
    out(ld(ans)/2);
}

int main(){
    int t = 1; //in(t);
    while (t--) { solve(); }
}