123123123

def f(x, y, last_cmd = None):
    if x > y:
        return 0
    if x == y:
        return 1
    if last_cmd == "C" and x < y:
        return f(x + 3, y, "B") * f(x * 4, y, "C")
    if x < y:
        return f(x + 2, y, "A") * f(x + 3, y, "B") * f(x * 4, y, "C")

print(f(1, 50))