#include <bits/stdc++.h>
using namespace std;
long long int fast_exp(long long int base, long long int exp1) {
  long long int res = 1;
  while (exp1 > 0) {
    if (exp1 & 1) res = (res * base) % 1000000007;
    base = (base * base) % 1000000007;
    exp1 /= 2;
  }
  return res % 1000000007;
}
long long int pr[1000001] = {0};
void isprime() {
  pr[0] = 1;
  pr[1] = 1;
  for (long long int a = 2; a * a <= 1000001; a++) {
    if (!pr[a]) {
      for (long long int b = a * a; b < 1000001; b += a) {
        pr[b] = 1;
      }
    }
  }
}
long long int comp = 1, tim = 0;
struct vertex {
  vector<long long int> adj;
  long long int vis = 0;
  long long int parent = -1;
  long long int dist = 0;
  long long int component = 0;
  long long int in = 0;
  long long int out = 0;
  long long int low = 0;
  long long int child = 0;
  long long int indeg = 0;
  long long int outdeg = 0;
  bool AP = false;
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, k;
  cin >> n >> k;
  long long int x[n];
  for (long long int a = 0; a < n; a++) cin >> x[a];
  string s;
  cin >> s;
  vector<long long int> v;
  v.push_back(x[0]);
  long long int ans = 0;
  for (long long int a = 1; a < s.length(); a++) {
    if (s[a] == s[a - 1]) {
      v.push_back(x[a]);
    } else {
      sort(v.begin(), v.end(), greater<long long int>());
      long long int po = v.size();
      for (long long int a = 0; a < min(po, k); a++) ans += v[a];
      v.clear();
      v.push_back(x[a]);
    }
  }
  long long int po = v.size();
  if (po) {
    sort(v.begin(), v.end(), greater<long long int>());
    for (long long int a = 0; a < min(po, k); a++) ans += v[a];
  }
  cout << ans << endl;
  return 0;
}
