#include <bits/stdc++.h>

using namespace std;

struct point {
    double x, y;
};

double square (point a, point b, point c) {
    b.x -= a.x;
    b.y -= a.y;
    c.x -= a.x;
    c.y -= a.y;
    return abs(b.x * c.y - b.y * c.x) / 2.;
}

double dist (point a, point b) {
    return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}

int main()
{
    cout << fixed << setprecision(9);
    point a, b, c;
    cin >> a.x >> a.y >> b.x >> b.y >> c.x >> c.y;
    cout << square(a, b, c);
}