By the time Agent P breaks into the evil Dr$.$ D$\text{'}$s private office, Dr$.$ D changes his computer's password and manages to escape.

Dr$.$ D changed some random letters in the original password to make the new password; therefore, the new password is the same length as the old one $($there is no insertion or deletion of characters$).$

The password is a string of characters, with the only possible characters being the small letters from the English alphabet $(\text{'}$a$\text{'}$ to $\text{'}$z$\text{'}).$

Agent P knows that the new password is k$-$balanced. A string is k$-$balanced if all the substrings of length k have the same counts of all the $26$ letters $(\text{'}$a$\text{'}$ to $\text{'}$z$\text{'})($see samples for more details$).$

A string A is a substring of a string B if A can be obtained from B by deletion of several $($possibly$,$ zero or all$)$ characters from the beginning and several $($possibly$,$ zero or all$)$ characters from the end. For example, $\text{'}$c$\text{'},$ 'fish', 'cat', 'atf', $\text{'}$is$\text{'},...,$ are substrings of 'catfish', but $\text{'}$z$\text{'},$ 'cis', 'cats',..., are not.

He also believes that Dr$.$ D was in a hurry and could not have changed many characters.

So$,$ he wants to know the minimum number of changes required in the old password to make it k$-$ balanced.

Given a string password and an integer k$.$ Help Agent P by calculating the minimum number of changes required in password so that the new password is k$-$balanced.

Input Format

The first line contains an integer, k$,$ denoting the integer described in the problem statement

The next line contains a string, password, denoting the old password

Constraints

$1<=$ k $<=$ len$($password$)$

$1<=$ len$($password$)<=10^5$

Case $1$:

Input:

$5$

bdbab

Output: $0$

Explanation:

k $=5$ password $=$ "bdbab" all the k$-$length substrings $=["$bdbab$"\}$ The count of each character is already the same in all the k$-$length substrings.

case: $2$

Input: baacb

Output:$2$

Explanation:

k $=4$ password $=$ "baacb" all the k$-$length substrings $=\{"$baac$",$ "aacb"$\}$ count of letters in "baac" is $\{"$a$"=2,"$b$"=1,"$c$"=1$