#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
int calc(vector<int>x, vector<int>y) {
	int dx0 = x[1] - x[0];
	int dx1 = x[2] - x[0];
	int dy0 = y[1] - y[0];
	int dy1 = y[2] - y[0];
	return abs(dx0* dy1 - dx1 * dy0);
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	vector<int>x(3), y(3);
	rep(i, 3)cin >> x[i] >> y[i];
	int ans = 0;
	const int dx[4] = { 1,0,-1,0 };
	const int dy[4] = { 0,-1,0,1 };
	rep(i, 4)rep(j, 4)rep(k, 4) {
		auto cx = x, cy = y;
		cx[0] += dx[i];
		cx[1] += dx[j];
		cx[2] += dx[k];
		cy[0] += dy[i];
		cy[1] += dy[j];
		cy[2] += dy[k];
		chmax(ans, calc(cx, cy));
	}
	if (0 == ans % 2)cout << ans / 2 << endl;
	else cout << ans / 2 << ".5" << endl;
	return 0;
}