#include <bits/stdc++.h>
using namespace std;
#include <atcoder/modint>
using namespace atcoder;
//using mint = modint998244353;
using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
template<class T> void unique(vector<T> &V) {V.erase(unique(V.begin(), V.end()), V.end());}
template<class T> void sortunique(vector<T> &V) {sort(V.begin(), V.end()); V.erase(unique(V.begin(), V.end()), V.end());}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)
template<class T> void printvec(vector<T> &V) {int N = V.size(); for (int i = 0; i < N; i++) cout << V[i] << (i == N - 1 ? '\n' : ' ');}
template<class T> void printvect(vector<T> &V) {for (auto v : V) cout << v << '\n';}
template<class T> void printvec2(vector<vector<T>> &V) {for (auto &v : V) printvec(v);}

int main()
{
  ll N;
  cin >> N;
  vector<ll> A(N);
  for (ll i = 0; i < N; i++)
  {
    cin >> A.at(i);
  }
  string S;
  cin >> S;

  vector<vector<ll>> nxt(N + 1, vector<ll>(26, -1));
  for (ll i = N - 1; i >= 0; i--)
  {
    for (ll j = 0; j < 26; j++)
    {
      if (S.at(i) - 'a' == j)
        nxt.at(i).at(j) = i;
      else
        nxt.at(i).at(j) = nxt.at(i + 1).at(j);
    }
  }

  vector dp(N + 1, vector(27, mint(0)));
  dp.at(0).at(26) = 1;
  for (ll i = 0; i < N + 1; i++)
  {
    for (ll j = 0; j < 27; j++)
    {
      for (ll nj = 0; nj < 26; nj++)
      {
        if (j == nj)
          continue;
        ll ni = nxt.at(i).at(nj) + 1;
        if (ni >= 1)
        {
          dp.at(ni).at(nj) += (A.at(ni - 1) - 1) * dp.at(i).at(j);
          dp.at(ni).at(26) += dp.at(i).at(j);
        }
      }
    }
  }

  mint ans = -1;
  for (ll i = 0; i < N + 1; i++)
  {
    for (ll j = 0; j < 27; j++)
    {
      mint tmp = dp.at(i).at(j);
      ans += tmp;

      /*
      if (tmp != 0)
        cerr << i << " " << j << "  " << dp.at(i).at(j).val() << endl;
      //*/
    }
  }
  cout << ans.val() << endl;
}