task 12

def f(a, b):
    if a > b:
        return 0
    if a == b:
        return 1
    if a < b:
        return f(a+1, b) + f(a+2, b) + f(a*3, b)

all_with_8 = f(1, 8)*f(8, 27)
without_10_11 = f(1, 8) * f(8, 10) * f(10, 11) * f(10, 11) * f(11, 27)
print(all_with_8 - without_10_11)