# import pypyjit
# pypyjit.set_param('max_unroll_recursion=-1')
from collections import defaultdict as dd
S = input
R = range
P = print
def I(): return int(S())
def M(): return map(int, S().split())
def L(): return list(M())
def O(): return list(map(int, open(0).read().split()))
def yn(b): print("Yes" if b else "No")
biga = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
smaa = "abcdefghijklmnopqrstuvwxyz"
def acc(a):
	b = [0]
	for i in a:
		b.append(b[-1] + i)
	return b

def area(x1, y1, x2, y2, x3, y3):
	x2 -= x1
	y2 -= y1
	x3 -= x1
	y3 -= y1
	return abs(x2 * y3 - x3 * y2)

x1, y1, x2, y2, x3, y3 = M()
ans = 0
for a, b in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
	for c, d in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
		for e, f in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
			ans = max(ans, area(x1 + a, y1 + b, x2 + c, y2 + d, x3 + e, y3 + f))
print(ans / 2)