text: #include <iostream>
  
  using namespace std;
  
  int main()
  {
      float Ax , Ay , Bx , By , Cx , Cy;
  
      cin >> Ax >> Ay >> Bx >> By >> Cx >> Cy;
  
      float area = 1.0 * (Ax * ( By - Cy) + Bx *(Cy - Ay) + Cx *(Ay - By))/ 2;
  
      if(area < 0)
          area = area * -1;
  
      cout << area << endl;
      return 0;
  }
  