#line 1 "cp_templates/template/template.hpp"
# include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const double pi = acos(-1);
template<class T>constexpr T inf() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T hinf() { return inf<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); }
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); }
template<class T> bool chmin(T& a,T b) { if(a > b){a = b; return true;} return false; }
template<class T> bool chmax(T& a,T b) { if(a < b){a = b; return true;} return false; }
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(ll n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(ll n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
ll gcd(ll a, ll b) { if (b == 0)return a; return gcd(b, a%b); };
ll lcm(ll a, ll b) { ll g = gcd(a, b); return a / g*b; };
ll MOD(ll x, ll m){return (x%m+m)%m; }
ll FLOOR(ll x, ll m) {ll r = (x%m+m)%m; return (x-r)/m; }
template<class T> using dijk = priority_queue<T, vector<T>, greater<T>>;
# define all(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        (wpwpw).erase(unique(all((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(all((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(all((rprpr)),(rprpr).begin(),TU<char>)
# define rep(i,upupu)         for(ll i = 0, i##_len = (upupu);(i) < (i##_len);(i)++)
# define reps(i,opopo)        for(ll i = 1, i##_len = (opopo);(i) <= (i##_len);(i)++)
# define len(x)                ((ll)(x).size())
# define bit(n)               (1LL << (n))
# define pb push_back
# define exists(c, e)         ((c).find(e) != (c).end())

struct INIT{
	INIT(){
		std::ios::sync_with_stdio(false);
		std::cin.tie(0);
		cout << fixed << setprecision(20);
	}
}INIT;

namespace mmrz {
	void solve();
}

int main(){
	mmrz::solve();
}
#line 2 "2790.cpp"
// #include "./cp_templates/template/debug.hpp"
// #define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
// #define debug(...) (static_cast<void>(0))

using namespace mmrz;

int s2(int x1, int y1, int x2, int y2, int x3, int y3){
	double a = x2-x1;
	double b = y2-y1;
	double c = x3-x1;
	double d = y3-y1;
	return abs(a*d - b*c);
}

void SOLVE(){
	int x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	int a2 = 0;
	reps(i, 4){
		if(i == 1)x1++;
		if(i == 2)x1--;
		if(i == 3)y1++;
		if(i == 4)y1--;
		reps(j, 4){
			if(j == 1)x2++;
			if(j == 2)x2--;
			if(j == 3)y2++;
			if(j == 4)y2--;
			reps(k, 4){
				if(k == 1)x3++;
				if(k == 2)x3--;
				if(k == 3)y3++;
				if(k == 4)y3--;
				chmax(a2, s2(x1, y1, x2, y2, x3, y3));
				if(k == 1)x3--;
				if(k == 2)x3++;
				if(k == 3)y3--;
				if(k == 4)y3++;
				
			}
			if(j == 1)x2--;
			if(j == 2)x2++;
			if(j == 3)y2--;
			if(j == 4)y2++;
		}
		if(i == 1)x1--;
		if(i == 2)x1++;
		if(i == 3)y1--;
		if(i == 4)y1++;
	}
	if(a2%2 == 0){
		cout << a2/2 << ".0" << endl;
	}else{
		cout << a2/2 << ".5" << endl;
	}
}

void mmrz::solve(){
	int t = 1;
	//cin >> t;
	while(t--)SOLVE();
}