Avoid stormy period (from September to November) since the stairs will grow to be slippery and you might drop when climbing the mountains.  trong m?t kho?n th?i gian nh?t ??nh tr??c khi ?i?u ch?nh, t?t nh?t b?n nên dùng ph??ng pháp t? ??ng ho?c xây d?ng hàm ?