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

a = [x1, y1]
b = [x2, y2]
c = [x3, y3]


def f(a1, b1, a2, b2, a3, b3):
    u0 = a2 - a1
    u1 = b2 - b1
    v0 = a3 - a1
    v1 = b3 - b1
    return abs(u1*v0 - v1*u0)

dx = [1, -1, 0, 0]
dy = [0, 0, 1, -1]

ans = 0

for i in range(4):
    for j in range(4):
        for k in range(4):
            ans = max(ans, f(x1+dx[i], y1+dy[i], x2+dx[j], y2+dy[j], x3+dx[k], y3+dy[k]))

print(ans/2)