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 ith, 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 ≤ 105). 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.

解题：贪心。

 #include <iostream>

 #include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <algorithm>

 #include <climits>

 #include <vector>

 #include <queue>

 #include <cstdlib>

 #include <string>

 #include <set>

 #include <stack>

 #define LL long long

 #define pii pair<int,int>

 #define INF 0x3f3f3f3f

 using namespace std;

 int letter[];

 char str[];

 bool cmp(const int &x,const int &y){

     return x > y;

 }

 int main() {

     int n,k;

     LL ans;

     while(~scanf("%d %d",&n,&k)){

         memset(letter,,sizeof(letter));

         scanf("%s",str);

         for(int i = ; str[i]; i++) letter[str[i]-'A']++;

         sort(letter,letter+,cmp);

         for(int i = ans = ; k && i < ; i++){

             ans += 1LL*min(k,letter[i])*min(k,letter[i]);

             k -= min(k,letter[i]);

         }

         cout<<ans<<endl;

     }

     return ;

 }