Codeforces Round #263 (Div. 2)B. Appleman and Card Game

#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <list>
#include <deque>
#include <queue>
#include <cctype>
#include <map>
#include <set>
#include <bitset>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdlib>
#include <ctime>
#include <cassert>
#include <limits>
#include <fstream>

using namespace std;

#define mem(A, X) memset(A, X, sizeof A)
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define all(x) x.begin(), x.end()
#define sz(x) (int)((x).size())
#define rep(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#define Rep(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define min3(a,b,c) min(a,min(b,c))
#define max3(a,b,c) max(a,max(b,c))
#define dbg(a) cout << a << endl;
#define fi first
#define se second
typedef long long int64;
int gcd(const int64 &a, const int64 &b) {return b == 0 ? a : gcd(b, a % b);}
int64 int64pow(int64 a, int64 b){if(b == 0) return 1;int64 t = int64pow(a, b / 2);if(b % 2) return t * t * a;return t * t;}
const int inf = 1 << 30;
const double eps = 1e-8;
const double pi = acos(-1.0);
const int MAX_N = 500005;

int64 n, k, ans;
string s;
map<char, int> m;

void solve()
{
    m.clear();
    ans = 0;
    cin >> s;
    rep(i, 0, sz(s)) {
        ++m[s[i]];
    }
    while (k > 0) {
       int64 MAX = -inf;
       int64 pos = -1;
       rep(i, 0, sz(m)) {
            if (MAX < m[i]) {
                 MAX = m[i];
                 pos = i;
            }
       }
       if (k <= MAX) {
            ans += k * k;
            k = 0;
       }
       if (k > MAX) {
            ans += MAX * MAX;
            k -= MAX;
            m[pos] = 0;
       }
    }
    cout << ans << endl;
}
int main()
{
    while (cin >> n >> k) {
        solve();
    }
    return 0;
}