what is the criteria?
To win a codechef t-shirt you need to finish into top 20 Indian contestants of Long Challenge held every month or you need to finish into the top 5 Indian contestants of short contest held every month. You can also win a t-shirt if you are in the top 5 contributors list at the end of a month.
but my one friend recently got a t-shirt by getting 4th position in this question http://www.codechef.com/SEPT14/problems/FACTORIZ