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

def calc_area(x1, y1, x2, y2, x3, y3):
    return abs((x1 - x3) * (y2 - y3) - (x2 - x3) * (y1 - y3)) / 2

directions = (-1, 0), (1, 0), (0, -1), (0, 1)
max_area = 0
for dx1, dy1 in directions:
    nx1 = x1 + dx1
    ny1 = y1 + dy1
    for dx2, dy2 in directions:
        nx2 = x2 + dx2
        ny2 = y2 + dy2
        for dx3, dy3 in directions:
            nx3 = x3 + dx3
            ny3 = y3 + dy3
            max_area = max(max_area, calc_area(nx1, ny1, nx2, ny2, nx3, ny3))

print(max_area)