Hi. I'm attempting to solve this problem: http://main.edu.pl/en/archive/pa/2011/naj (it belongs to the competition 'Algorithmic Engagements 2011')

Summary: Given a long string find the length of the shortest period of the resulting string after removing a single character (A string *t* is a period of *s* iff *s* is a preffix of *t*^{k} for some *k*)

I can't see a way faster than O(N^2) (based on KMP). Could you give me a hint for a faster solution ?

Regards.