#include <bits/stdc++.h>
using namespace std;
int n;
long long dp[4];
int a[100005];
string s;
int main() {
  cin >> n;
  cin >> s;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (s[i] == 'h')
      dp[0] += a[i];
    else if (s[i] == 'a')
      dp[1] = min(dp[0], dp[1] + a[i]);
    else if (s[i] == 'r')
      dp[2] = min(dp[1], dp[2] + a[i]);
    else if (s[i] == 'd')
      dp[3] = min(dp[2], dp[3] + a[i]);
  }
  cout << dp[3];
  return 0;
}
