Extracting characters from a URL

Hello everyone,

I have an URL in which I'd like to extract only a few part of it.
Example:

http://amazon.com/gp/product/B000BNCA4K/ref=as_li_tl?tag=pollylolitop-20

I need to omit few characters in the URL.
The output has to be

http://amazon.com/gp/product/B000BNCA4K/

Someone please help me.
Thanks in advance.