x1,y1,x2,y2,x3,y3=map(int,input().split())
def f(a,b,c,d):
  ans=abs(a*d-b*c)
  return ans/2
from itertools import product
result=0
for A in product(range(4),repeat=3):
  v=[x1,y1,x2,y2,x3,y3]
  for i in range(3):
    if A[i]==0:
      v[2*i]-=1
    elif A[i]==1:
      v[2*i]+=1
    elif A[i]==2:
      v[2*i+1]+=1
    else:
      v[2*i+1]-=1
  a,b,c,d=v[2]-v[0],v[3]-v[1],v[4]-v[0],v[5]-v[1]
  ans=f(a,b,c,d)
  result=max(result,ans)
print(result)