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


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


ans = 0
dydx = [(0, 1), (0, -1), (1, 0), (-1, 0)]

for dx1, dy1 in dydx:
    for dx2, dy2 in dydx:
        for dx3, dy3 in dydx:
            ans = max(ans, S(x1 + dx1, y1 + dy1, x2 +
                      dx2, y2 + dy2, x3 + dx3, y3 + dy3))

print(ans / 2)