#include <iostream>
#include <cmath>
#include <cstdio>
using namespace std;

int main()
{
    double x[3];
    double y[3];
    while (cin >> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2]){
      //行列式算法
      double a=x[1]-x[0];
      double b=x[2]-x[0];
      double c=y[1]-y[0];
      double d=y[2]-y[0];
      double s=abs(a*d-c*b)/2.0;
      printf("%.2f\n",s);
    }
  return 0;
}