x1, y1, x2, y2, x3, y3 = map(int, input().split())
P1, P2, P3 = (x1, y1), (x2, y2), (x3, y3)


def adj(P):
   x, y = P
   res = []
   for dx in -1, 0, 1:
      for dy in -1, 0, 1:
         if dx*dy == 0 and dx+dy != 0:
            res.append((x+dx, y+dy))
   return res


def area(P, Q, R):
   x, y = P
   a, b = Q
   c, d = R
   a, b = a-x, b-y
   c, d = c-x, d-y
   return abs(a*d - b*c)


cands = []
for P in adj(P1):
   for Q in adj(P2):
      for R in adj(P3):
         cands.append(area(P, Q, R))

ans = max(cands) / 2
print(ans)