SP8991 GUESSLNK - Number Guessing Game 2

I really enjoy setting problem [GUESSING](/problems/GUESSING/). After three years, I decided to set another "kind of interactive" problem based on it. Given a link for GUESSING problem, find the server's response

each line contains a link in format "http://www.spoj.com/problems/GUESSING/XXXXXXYYYYYY/", where XXXXXXYYYYYY contains exactly 12 digit.

The server's response, in format "XAYB".