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

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

for i in range(4):
    xi = x1 + dx[i]
    yi = y1 + dy[i]
    for j in range(4):
        xj = x2 + dx[j]
        yj = y2 + dy[j]
        for k in range(4):
            xk = x3 + dx[k]
            yk = y3 + dy[k]
            area = abs((xj - xi) * (yk - yi) - (xk - xi) * (yj - yi))
            max_area = max(max_area, area)

print(max_area / 2)