Untitled

def f(x, y,z):
    if x < y:
        return 0
    if x == y:
        return z[1] == 'B' and z[-3] == 'C' and len(z) >= 5
    if x > y:
        return f(x - 1, y,z + 'A') + f(x - 5, y,z + 'B') + f(x // 3, y,z +'C')


print(f(33, 4))