How to Find Wps Pin of Connected Wifi Without Accessing the Router?

how to find wps pin of connected wifi without accessing the router. My pc is connected to a wifi network but I cannot access the router through the default username and password. If anyone know an easy way to crack/hack the router access password then let me know. I need it because if my neighbor change the password then I can't ask again and again. Beside this i want to learn it for educational purposes. Thanks in advance.