#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i, n) for(ll i = 0; i < (n); i++)
#define reps(i, l, r) for(ll i = (l); i < (r); i++)
#define all(a) (a).begin(), (a).end()
#define endl "\n";
const ll INF = 2e18;
const ll mod1 = 1000000007;
const ll mod2 = 998244353;
ll dx[4] = {-1, 1, 0, 0};
ll dy[4] = {0, 0, -1, 1};
void chmin(ll& a, ll b){ if(a > b) a = b; }
void chmax(ll& a, ll b){ if(a < b) a = b; }
ll gcd(ll a, ll b) {return (b == 0 ? a : gcd(b, a % b));}
ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
void solve() {
	//ofstream cout("text.txt");
    ll x1, y1, x2, y2, x3, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    ld ans = 0;
    rep(i, 4) {
        rep(j, 4) {
            rep(k, 4) {
                x1 += dx[i]; x2 += dx[j]; x3 += dx[k];
                y1 += dy[i]; y2 += dy[j]; y3 += dy[k];
                ll Dx1 = x1 - x2, Dx2 = x3 - x2;
                ll Dy1 = y1 - y2, Dy2 = y3 - y2;
                ld sum = (ld)abs(Dx1 * Dy2 - Dx2 * Dy1) / (ld)2;
                ans = max(ans, sum);
                x1 -= dx[i]; x2 -= dx[j]; x3 -= dx[k];
                y1 -= dy[i]; y2 -= dy[j]; y3 -= dy[k];
            }
        }
    }
    cout << fixed << setprecision(1) << ans << endl;
}
signed main() {
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
  ll T = 1; //cin >> T;
  while(T--) solve();
}