Given a palindrome of length N consisting only of lowercase letters , output the minimum possible length of palindrome which can be formed by deleting the characters of the original string . However there is a catch , the required palindrome should contain atleast 1 occurence of all the unique characters in the original string .

INPUT :

The first line of input contains a single integer N, denoting length of string .

The second line of input contains a string S.

OUTPUT :

Output a single integer , the required length of palindrome .

CONSTRAINTS :

$1 \leq N \leq 500$