#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back

using namespace std;
typedef long long ll;

const int MOD = 1e9 + 7;
const int mxP = 1e2 + 9;
const int mxN = 1e5 + 9;
const int INF = 1e7 + 7;
const int mxK = 20;
const double eps = 1e-7;

ll c[30], dp[mxN], last[30], segTree[4 * mxN];

void updateTree (ll v, ll l, ll r, ll idx, ll value) {
    if (l == r) {
        segTree[v] = value;

        return;
    }

    ll mid = (l + r) / 2;
    if (idx <= mid)
        updateTree (2 * v, l, mid , idx, value);
    else updateTree (2 * v + 1, mid + 1, r, idx, value);

    return;
}

ll getMin (ll v, ll l, ll r, ll L, ll R) {
    if (L <= l && r <= R)
        return segTree[v];

    if (r < L || l > R)
        return ll (1e17);

    ll mid = (l + r) / 2;
    ll lm = getMin (2 * v, l, mid, L, R);
    ll rm = getMin (2 * v + 1, mid + 1, r, L, R);

    return min (lm, rm);
}

void solve () {
    ll n;
    cin >> n;

    string s;
    cin >> s;
    s = "3" + s;
    s += "a";

    int m;
    cin >> m;

    for (ll i = 1; i <= m; i++)
        cin >> c[i];

    last[s[1] - 'a'] = 1;
    for (ll i = 2; i <= n + 1; i++) {
        vector <ll> v;

        v.pb (0);
        for (ll i = 0; i < m; i++) {
            if (last[i] != 0)
                v.pb (last[i]);
        }

        sort (v.begin(), v.end());

        dp[i] = 1e9;
        for (ll j = 1; j < (ll) v.size(); j++) {
            dp[i] = min (dp[i], c[v.size() - j] + getMin (1, 1, n, v[j - 1] + 1, v[j]));
        }

        //cout << i << ' ' << dp[i] << "\n";
        updateTree (1, 1, n, i, dp[i]);
        last[s[i] - 'a'] = i;
    }

    cout << dp[n + 1] << "\n";
    return;
}

int main () {
    ll t = 1;
    //cin >> t;

    //preCalc ();
    while (t--)
        solve ();

    return 0;
}

/*
 *
 *4
abcd
 26
2 3 5 10 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
 *
 *
 *
 *
 */