#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;

int main() {
	lint x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

	lint a=0, b=0, c=0, x, y, z;
	int dx[4] = {1, -1, 0, 0};
	int dy[4] = {0, 0, 1, -1};
	rep(i, 4) {
		rep(j, 4) {
			rep(k, 4) {
				x = x1+dx[i];
				y = y1+dy[i];
				chmax(a, abs((x2+dx[j]-x)*(y3+dy[k]-y) - (x3+dx[k]-x)*(y2+dy[j]-y)));
			}
		}
	}
	cout << fixed << setprecision(10) << (double)a/2 << endl;
}