hdu 67

import java.util.*;

public class Main {

  public static void main(String args[]){

 Scanner cin=new Scanner(System.in);

 

 Double result=0.00d;

  while(true){

    Double x0= cin.nextDouble();    

    Double y0= cin.nextDouble();   

    Double x1= cin.nextDouble();   

    Double y1= cin.nextDouble();   

    Double x2= cin.nextDouble();   

    Double y2= cin.nextDouble();

    if(x0 y0 x1 y1 x2 y2==0) break;

    result = ((x1-x0)*(y2-y0)-(x2-x0)*(y1-y0))/2;

    result=Math.abs(result);

     

      java.text.DecimalFormat myformat=new java.text.DecimalFormat("0.0");

      String str = myformat.format(result);    

    System.out.println(str);

 

   }

 

  }

  

}

 

#include

#include

int main()

{

  int a,b,c,d,e,r,s;

  while(1)

  {

 scanf("%d %d %d %d %d %d",&a,&b,&c,&d,&e,&r);

 if(a==0&&b==0&&c==0&&d==0&&e==0&&r==0)   return 0;

   s=(a*d+b*e+c*r)-(a*r+d*e+b*c);

  if(s<0)   s=-s;

    printf("%.1f\n",s/2.0);

  

  }return 0;

}