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

def s(x1,y1,x2,y2):
  ret = x1*y2-x2*y1
  if ret<0:
    ret *= -1
  return ret/2

dx=[1,0,-1,0]
dy=[0,1,0,-1]

ans = 0

for i in range(4):
  for j in range(4):
    for k in range(4):
      x4=x1+dx[i]
      y4=y1+dy[i]
      x5=x2+dx[j]
      y5=y2+dy[j]
      x6=x3+dx[k]
      y6=y3+dy[k]
      ss=s(x5-x4,y5-y4,x6-x4,y6-y4)
      ans=max(ans,ss)
print(ans)