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

def maxtring(x1, y1, x2, y2, x3, y3):
    maxa = 0
    
    for op1 in [0, 1, 2, 3, 4]:
        for op2 in [0, 1, 2, 3, 4]:
            for op3 in [0, 1, 2, 3, 4]:
                new_x1, new_y1 = apply(x1, y1, op1)
                new_x2, new_y2 = apply(x2, y2, op2)
                new_x3, new_y3 = apply(x3, y3, op3)
                
                area = triangle(new_x1, new_y1, new_x2, new_y2, new_x3, new_y3)
                maxa = max(maxa, area)
    
    return maxa

def apply(x, y, op):
    if op == 1:
        return x + 1, y
    elif op == 2:
        return x - 1, y
    elif op == 3:
        return x, y + 1
    elif op == 4:
        return x, y - 1
    else:
        return x, y

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