import itertools

def triangle_area(A, B, C):
    x1, y1 = A
    x2, y2 = B
    x3, y3 = C
    return abs((x1*(y2-y3) + x2*(y3-y1) + x3*(y1-y2)) / 2)

def max_triangle_area(A, B, C):
    max_area = 0
    operations = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    
    for op_A in operations:
        new_A = (A[0] + op_A[0], A[1] + op_A[1])
        for op_B in operations:
            new_B = (B[0] + op_B[0], B[1] + op_B[1])
            for op_C in operations:
                new_C = (C[0] + op_C[0], C[1] + op_C[1])
                area = triangle_area(new_A, new_B, new_C)
                if area > max_area:
                    max_area = area

    return max_area

a,aa,b,bb,c,cc = list(map(int, input().split(' ')))
A = (a,aa)
B = (b,bb)
C = (c,cc)
print(max_triangle_area(A, B, C))