文件目录

#include <bits/stdc++.h>
using namespace std;

int main()
{
    double x1, y1, x2, y2, x3, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    double a, b, c, ax = x2 - x1, ay = y2 - y1, bx = x3 - x2, by = y3 - y2, cx = x1 - x3, cy = y1 - y3;
    a = sqrt(ax * ax + ay * ay);
    b = sqrt(bx * bx + by * by);
    c = sqrt(cx * cx + cy * cy);
    double p = (a + b + c) / 2;
    printf("%.2lf", sqrt(p * (p - a) * (p - b) * (p - c)));
    return 0;
}