x1,y1,x2,y2,x3,y3=map(int,input().split())

def f(x1,y1,x2,y2,x3,y3):
  S=abs(x1*y2 + x2*y3 + x3*y1 - y1*x2 - y2*x3 - y3*x1)/2
  return S
    
dxy=[(1,0),(-1,0),(0,1),(0,-1)]
ans=0
for dx,dy in dxy:
  for dx2,dy2 in dxy:
    for dx3,dy3 in dxy:
      ans=max(ans,f(x1+dx,y1+dy,x2+dx2,y2+dy2,x3+dx3,y3+dy3))
print(ans)