#include <bits/stdc++.h>
using namespace std;
void USACO(string s) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  freopen((s + ".in").c_str(), "r", stdin);
  freopen((s + ".out").c_str(), "w", stdout);
}
const long long MAXN = 5010;
void solve() {
  long long n;
  string s;
  cin >> n;
  cin >> s;
  long long a[n];
  for (long long i = 0; i < n; i++) cin >> a[i];
  long long dp[n][4];
  memset(dp, 0, sizeof(dp));
  dp[0][0] = (s[0] != 'h' ? 0 : a[0]);
  dp[0][1] = (s[0] == 'h' ? 0 : 1e15);
  dp[0][2] = dp[0][3] = 1e15;
  for (long long i = 1; i < n; i++) {
    dp[i][0] = dp[i][1] = dp[i][2] = dp[i][3] = 1e15;
    dp[i][0] = dp[i - 1][0] + (s[i] == 'h' ? a[i] : 0);
    if (s[i] == 'h') dp[i][1] = dp[i - 1][0];
    dp[i][1] = min(dp[i][1], dp[i - 1][1] + (s[i] == 'a' ? a[i] : 0));
    if (s[i] == 'a') dp[i][2] = dp[i - 1][1];
    dp[i][2] = min(dp[i][2], dp[i - 1][2] + (s[i] == 'r' ? a[i] : 0));
    if (s[i] == 'r') dp[i][3] = dp[i - 1][2];
    dp[i][3] = min(dp[i][3], dp[i - 1][3] + (s[i] == 'd' ? a[i] : 0));
  }
  cout << min(min(dp[n - 1][0], dp[n - 1][1]), min(dp[n - 1][2], dp[n - 1][3]))
       << "\n";
}
int main() { solve(); }
