import math
if __name__=='__main__':
    ar=str.split(input())
    x1=float(ar[0]);y1=float(ar[1])
    ar=str.split(input())
    x2=float(ar[0]);y2=float(ar[1])
    ar=str.split(input())
    x3=float(ar[0]);y3=float(ar[1])
    a=math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))
    b=math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3))
    c=math.sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2))
    p=(a+b+c)/2.
    print('%.2f\n'%(math.sqrt(p*(p-a)*(p-b)*(p-c))))