#include <bits/stdc++.h>
using namespace std;

int n, k;
long long a[200002], ans;
char ch[200002];
vector<long long> s;

int main()
{
  cin >> n >> k;
  for (int i = 1; i <= n; i++)
    cin >> a[i];
  cin >> (ch + 1);
  for (int i = 1; i <= n + 1; i++){
    if (ch[i] != ch[i - 1]){
      sort(s.begin(), s.end());
      reverse(s.begin(), s.end());
      for (int j = 0; j < min((int)s.size(), k); j++)
        ans += s[j];
      s.clear();
    }
    s.push_back(a[i]);
  }
  cout << ans;
  return 0;
}