#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using mint = atcoder::modint1000000007;
istream& operator>>(istream& is, mint& a) {
    int t; is >> t; a = t;
    return is;
}
ostream& operator<<(ostream& os, mint a) {
    return os << a.val();
}
#endif
#ifdef DEBUG
#define _GLIBCXX_DEBUG
#else
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast,unroll-loops")
#define cerr if (false) cerr
#undef assert
#define assert(...) void(0)
#undef endl
#define endl '\n'
#endif
#define overload3(a, b, c, name, ...) name
#define rep1(n) for (int i = 0; i < n; i++)
#define rep2(i, n) for (int i = 0; i < n; i++)
#define rep3(i, a, b) for (int i = a; i < b; i++)
#define rep(...) overload3(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)
#define per1(n) for (int i = n - 1; i >= 0; i--)
#define per2(i, n) for (int i = n - 1; i >= 0; i--)
#define per3(i, a, b) for (int i = b - 1; i >= (a); i--)
#define per(...) overload3(__VA_ARGS__, per3, per2, per1)(__VA_ARGS__)
#define ALL(a) a.begin(), a.end()
#define vec vector
#undef long
#define long long long
template<typename T>
ostream& operator<<(ostream& os, vector<T> a) {
    const int n = a.size();
    rep(i, n) os << a[i] << " \n"[i + 1 == n];
    return os;
}
template<typename T, size_t n>
ostream& operator<<(ostream& os, array<T, n> a) {
    rep(i, n) os << a[i] << " \n"[i + 1 == n];
    return os;
}
template<typename T>
istream& operator>>(istream& is, vector<T>& a) {
    for (T& i : a) is >> i;
    return is;
}
template<typename T>
bool chmin(T& x, T y) {
    if (x > y) { x = y; return true; }
    return false;
}
template<typename T>
bool chmax(T& x, T y) {
    if (x < y) { x = y; return true; }
    return false;
}
template<typename T>
void operator++(vector<T>& a) {
    for (T& i : a) ++i;
}
template<typename T>
void operator--(vector<T>& a) {
    for (T& i : a) --i;
}
template<typename T>
void operator++(vector<T>& a, int) {
    for (T& i : a) i++;
}
template<typename T>
void operator--(vector<T>& a, int) {
    for (T& i : a) i--;
}
void solve()
{
    int n; cin >> n;
    vec<mint> a(n); cin >> a;
    string s; cin >> s;
    vec<mint> d(n + 1);
    atcoder::fenwick_tree<mint> fw(n + 1);
    d[0] = 1;
    fw.add(0, 1);
    array<int, 26> pre = {};
    rep(i, n) {
        const int c = s[i] - 'a';
        mint val = d[pre[c]] + fw.sum(pre[c] + 1, i + 1);
        d[i + 1] = val;
        fw.add(i + 1, val * a[i]);
        pre[c] = i + 1;
    }
    cout << fw.sum(1, n + 1) << endl;
}
int main()
{
    srand((unsigned)time(NULL));
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(40);
    int t = 1;
    // cin >> t;
    while (t--)
        solve();
    return 0;
}