require "matrix"
xs = gets.split.map(&:to_f)
def f(x, y)
	[[x - 1, y], [x + 1, y], [x, y + 1], [x, y - 1]]
end
a, b, c = (0 ... 3).map { |i| f(*xs[2 * i, 2]) }
ans = 0.0
a.product(b, c).each do |p, q, r|
	p = Vector[*p, 0]
	q = Vector[*q, 0]
	r = Vector[*r, 0]
	ans = [ans, (p - q).cross(r - q)[2].abs * 0.5].max
end
p ans