#include <algorithm>
#include <cmath>
#include <iostream>

using namespace std;

// 三角形の面積を計算する関数
double calculate_area(int x1, int y1, int x2, int y2, int x3, int y3) {
    return abs(x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)) / 2.0;
}

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

    int operations[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
    double max_area = 0;

    for(int i = 0; i < 4; ++i) {
        for(int j = 0; j < 4; ++j) {
            for(int k = 0; k < 4; ++k) {
                int new_x1 = x1 + operations[i][0],
                    new_y1 = y1 + operations[i][1];
                int new_x2 = x2 + operations[j][0],
                    new_y2 = y2 + operations[j][1];
                int new_x3 = x3 + operations[k][0],
                    new_y3 = y3 + operations[k][1];

                double area = calculate_area(new_x1, new_y1, new_x2, new_y2,
                                             new_x3, new_y3);
                max_area = max(max_area, area);
            }
        }
    }

    cout << max_area << endl;
    return 0;
}