#include <bits/stdc++.h> using namespace std; struct point { double x, y; point(double A, double B) { x = A, y = B; } point() = default; }; struct triangle { point a, b, c; triangle(point A, point B, point C) { a = A, b = B, c = C; } triangle() = default; }; double getArea(triangle T) { // TODO: 计算三角形T的面积 return abs((T.b.x - T.a.x) * (T.c.y - T.a.y) - (T.b.y - T.a.y) * (T.c.x - T.a.x)) / 2.0; } int main() { int x, y; cin >> x >> y; point a(x, y); cin >> x >> y; point b(x, y); cin >> x >> y; point c(x, y); triangle T(a, b, c); cout << fixed << setprecision(2) << getArea(T) << endl; return 0; }