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

def distance(x1, y1, x2, y2):
    return ((x2-x1)**2 + (y2-y1)**2) ** 0.5

def size(a, b, c):
    s = (a+b+c)/2
    return (s*(s-a)*(s-b)*(s-c))**0.5

def func(n, x, y):
    if n == 0:
        return x+1, y
    elif n == 1:
        return x-1, y
    elif n == 2:
        return x, y+1
    else:
        return x, y-1

ans = 0
for i in range(4):
    for j in range(4):
        for k in range(4):
            X1, Y1 = func(i, x1, y1)
            X2, Y2 = func(j, x2, y2)
            X3, Y3 = func(k, x3, y3)
            ans = max(ans, size(distance(X1, Y1, X2, Y2), distance(X2, Y2, X3, Y3), distance(X3, Y3, X1, Y1)))

print(ans)