import math x1,y1=map(float,input().split()) x2,y2=map(float,input().split()) x3,y3=map(float,input().split()) a=abs(x1-x2) b=abs(x1-x3) c=abs(x2-x3) d=abs(y1-y2) e=abs(y1-y3) f=abs(y2-y3) g=aa+dd h=bb+ee i=cc+ff p=(g+h+i)/2 s=math.sqrt(p*(p-g)(p-h)(p-i)) print(s)