#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

int main() {
    vector<int> x(3), y(3);
    for (int i = 0; i < 3; i++) {
        cin >> x[i] >> y[i];
    }

    double ans = 0;
    auto dfs = [&](auto&& dfs, int idx, vector<int> X, vector<int> Y) -> void {
        if (idx == 3) {
            double res = abs((X[0] - X[2]) * (Y[1] - Y[2]) - (X[1] - X[2]) * (Y[0] - Y[2]));
            res /= 2;
            ans = max(ans, res);
            return;
        }

        X.push_back(x[idx]);
        Y.push_back(y[idx]);
        X.back()--;
        dfs(dfs, idx + 1, X, Y);
        X.back()++;
        X.back()++;
        dfs(dfs, idx + 1, X, Y);
        X.back()--;
        Y.back()--;
        dfs(dfs, idx + 1, X, Y);
        Y.back()++;
        Y.back()++;
        dfs(dfs, idx + 1, X, Y);
        Y.back()--;
    };

    vector<int> X, Y;
    dfs(dfs, 0, X, Y);

    printf("%.10lf\n", ans);
}