def tria(x1,y1,x2,y2,x3,y3):
  nx1 = x2-x1
  ny1 = y2-y1
  nx2 = x3-x1
  ny2 = y3-y1
  return abs(nx1*ny2-nx2*ny1)

a,b,c,d,e,f = map(int,input().split())

DD=((0,1),(1,0),(0,-1),(-1,0))

MAX=[]

for da,db in DD:
  for dc,dd in DD:
    for de,df in DD:
      que=(a+da,b+db,c+dc,d+dd,e+de,f+df)
      MAX.append(tria(*que))

print(max(MAX)/2)