#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#ifdef LOCAL
#include <algo/debug.h>
#else
#define debug(...) void(0)
#endif
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    fixed(cout).precision(12);
    auto calc = [](int x1, int y1, int x2, int y2, int x3, int y3) -> ld {
        int a1 = x2 - x1, b1 = y2 - y1;
        int a2 = x3 - x1, b2 = y3 - y1;
        return abs(a1 * b2 - a2 * b1) / ld(2);
    };
    ld ans = 0;
    int x1, y1, x2, y2, x3, y3; cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    for(int i = 0; i < 4; i++) {
        for(int j = 0; j < 4; j++) {
            for(int k = 0; k < 4; k++) {
                ans = max(ans, calc(x1 + dx[i], y1 + dy[i], x2 + dx[j], y2 + dy[j], x3 + dx[k], y3 + dy[k]));
            }
        }
    }
    cout << ans << endl;
}