#pragma GCC target("avx2")
#pragma GCC optimize("Ofast,unroll-loops")
// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using mint = atcoder::modint998244353;
istream &operator>>(istream &is, mint &a)
{
	long t;
	is >> t;
	a = t;
	return is;
}
ostream &operator<<(ostream &os, mint a)
{
	return os << a.val();
}
#endif
typedef long double ldouble;
#undef long
#define long long long
#define overload3(a, b, c, name, ...) name
#define rep1(n) for (long i = 0; i < n; i++)
#define rep2(i, n) for (long i = 0; i < n; i++)
#define rep3(i, a, b) for (long i = a; i < b; i++)
#define rep(...) overload3(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)
#define per1(n) for (long i = n - 1; i >= 0; i--)
#define per2(i, n) for (long i = n - 1; i >= 0; i--)
#define per3(i, a, b) for (long i = b - 1; i >= (a); i--)
#define per(...) overload3(__VA_ARGS__, per3, per2, per1)(__VA_ARGS__)
#define ALL(a) a.begin(), a.end()
#define vec vector
template <typename T>
ostream &operator<<(ostream &os, vector<T> &a)
{
	const int n = a.size();
	rep(i, n)
	{
		os << a[i];
		if (i + 1 != n)
			os << " ";
	}
	return os;
}
template <typename T, size_t n>
ostream &operator<<(ostream &os, array<T, n> &a)
{
	rep(i, n)
	{
		os << a[i];
		if (i + 1 != n)
			os << " ";
	}
	return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &a)
{
	for (T &i : a)
		is >> i;
	return is;
}
template <typename T, typename S>
bool chmin(T &x, S y)
{
	if (x > (T)y)
	{
		x = (T)y;
		return true;
	}
	return false;
}
template <typename T, typename S>
bool chmax(T &x, S y)
{
	if (x < (T)y)
	{
		x = (T)y;
		return true;
	}
	return false;
}
template <typename T>
void operator++(vector<T> &a)
{
	for (T &i : a)
		++i;
}
template <typename T>
void operator--(vector<T> &a)
{
	for (T &i : a)
		--i;
}
template <typename T>
void operator++(vector<T> &a, int)
{
	for (T &i : a)
		i++;
}
template <typename T>
void operator--(vector<T> &a, int)
{
	for (T &i : a)
		i--;
}
#undef endl
#define endl '\n'
vec<pair<int, int>> c(int x, int y)
{
	vec<pair<int, int>> res;
	res.push_back({x - 1, y});
	res.push_back({x + 1, y});
	res.push_back({x, y - 1});
	res.push_back({x, y + 1});
	return res;
}
int f(int x1, int y1, int x2, int y2, int x3, int y3)
{
	int xx1 = x2 - x1, yy1 = y2 - y1;
	int xx2 = x3 - x1, yy2 = y3 - y1;
	return abs(xx1 * yy2 - xx2 * yy1);
}
void solve()
{
	vec<int> a(6);
	cin >> a;
	int ans = 0;
	for (auto [x1, y1] : c(a[0], a[1]))
	{
		for (auto [x2, y2] : c(a[2], a[3]))
		{
			for (auto [x3, y3] : c(a[4], a[5]))
			{
				chmax(ans, f(x1, y1, x2, y2, x3, y3));
			}
		}
	}
	cout << ans / 2. << endl;
}
int main()
{
	// srand((unsigned)time(NULL));
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout << fixed << setprecision(40);
	int t = 1;
	// cin >> t;
	while (t--)
		solve();
	return 0;
}