#include <bits/stdc++.h>
using namespace std;
int N, K;
int A[202020];
string S;
void solve() {
  int i, j, k, l, r, x, y;
  string s;
  cin >> N >> K;
  for (i = 0; i < (N); i++) cin >> A[i];
  cin >> S;
  signed long long ret = 0;
  for (i = 0; i < N;) {
    j = i;
    vector<int> V;
    while (j < N && S[i] == S[j]) {
      V.push_back(A[j]);
      j++;
    }
    i = j;
    sort((V.begin()), (V.end()));
    reverse((V.begin()), (V.end()));
    for (j = 0; j < (min(K, (int)V.size())); j++) ret += V[j];
  }
  cout << ret << endl;
}
int main(int argc, char** argv) {
  string s;
  int i;
  if (argc == 1) ios::sync_with_stdio(false), cin.tie(0);
  for (i = 0; i < (argc - 1); i++) s += argv[i + 1], s += '\n';
  for (i = 0; i < (s.size()); i++) ungetc(s[s.size() - 1 - i], stdin);
  cout.tie(0);
  solve();
  return 0;
}
