task 14

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


print(f(2, 9) * f(9, 11) * f(11, 12))