Statement

Edoardo is trying to build a "customized" version of the Hollywood sign: same massive size but different text! The sign is going to be used on the hill of his small town in Italy, Pordenone. He managed to buy a sign S, but he would like to modify its letters in an optimal way so that the sign ends up having a substring repeating a same letter which is as long as possible. In order to change such a large wooden sign, Edoardo is asking for his Falegname Di Fiducia's help. The rate charged by the FDF is quite peculiar: he will charge 2^j - i + 1 euro to change the letters of each contiguous substring S[i … j] in the sign. For example, if the sign was aaxyaa and Edoardo wanted to change the substring S[3 … 4] from xy to aa, he would have to pay 2^2 = 4 euro. Asking the FDF to change one character at a time is not allowed: Edoardo must choose which characters he wants to change, and then the FDF will charge him according to the contiguous substrings selected...