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

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

ansl = []
for dx1, dy1 in [(0, -1), (0, 1), (-1, 0), (1, 0)]:
    for dx2, dy2 in [(0, -1), (0, 1), (-1, 0), (1, 0)]:
        for dx3, dy3 in [(0, -1), (0, 1), (-1, 0), (1, 0)]:
            candi = f(x1 + dx1, y1 + dy1, x2 + dx2, y2 + dy2, x3 + dx3, y3 + dy3)
            ansl.append(candi)

print(max(ansl)/2)