CF462B.Appleman and Card Game

Appleman has $n$ cards. Each card has an uppercase letter written on it. Toastman must choose $k$ cards from Appleman's cards. Then Appleman should give Toastman some coins depending on the chosen cards. Formally, for each Toastman's card $i$ you should calculate how much Toastman's cards have the letter equal to letter on $i$ th, then sum up all these quantities, such a number of coins Appleman should give to Toastman.

Given the description of Appleman's cards. What is the maximum number of coins Toastman can get?

The first line contains two integers $n$ and $k$ ( $1<=k<=n<=10^{5}$ ). The next line contains $n$ uppercase letters without spaces — the $i$ -th letter describes the $i$ -th card of the Appleman.

Print a single integer – the answer to the problem.

In the first test example Toastman can choose nine cards with letter D and one additional card with any letter. For each card with D he will get 9 coins and for the additional card he will get 1 coin.