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?

Appleman 有 $n$ 张卡片，每张卡片上写有一个大写字母。Toastman 必须从 Appleman 的卡片中选出 $k$ 张。随后，Appleman 将根据 Toastman 所选的卡片给予他若干枚硬币。形式化地，对于 Toastman 所选的第 $i$ 张卡片，需计算 Toastman 所选卡片中字母与该卡片上字母相同的卡片数量，再将所有这些数量求和；此总和即为 Appleman 应给予 Toastman 的硬币数。

已知 Appleman 所有卡片的描述，问：Toastman 最多能获得多少枚硬币？

The first line contains two integers n and k (1 ≤ k ≤ n ≤ 105). The next line contains n uppercase letters without spaces — the i-th letter describes the i-th card of the Appleman.

第一行包含两个整数 $n$ 和 $k$（$1 \leq k \leq n \leq 10^5$）。下一行包含 $n$ 个大写字母，中间无空格——其中第 $i$ 个字母表示 Appleman 的第 $i$ 张卡片。

Print a single integer – the answer to the problem.

输出一个整数——该问题的答案。

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.

在第一个测试样例中，Toastman 可以选择九张字母为 D 的卡片和一张任意字母的额外卡片。对于每张字母为 D 的卡片，他将获得 9 枚硬币；对于那张额外卡片，他将获得 1 枚硬币。