#include <bits/stdc++.h>
 
using namespace std;
 
int main() 
{
	int n, k;
	cin >> n >> k;
	vector<int> a(n);
	for (int i = 0; i < n; ++i) cin >> a[i];
	string s;
	cin >> s;
	long long ans = 0;
	for (int i = 0; i < n; ++i) 
	{
		int j = i;
		vector<int> vals;
		while (j < n && s[i] == s[j]) 
		{
			vals.push_back(a[j]);
			++j;
		}
		sort(vals.rbegin(), vals.rend());
		ans += accumulate(vals.begin(), vals.begin() + min(k, int(vals.size())), 0ll);
		i = j - 1;
	}
	cout << ans << endl;
	return 0;
}

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