#include <bits/stdc++.h>
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
ll mod=1e9+7;
#define rep(i,a) for (ll i=0;i<a;i++)



//おちこんだりもしたけれど、私はげんきです。
int main() {
	int N;
	cin>>N;
	vector<ll> A(N);
	string S;
	rep(i,N) cin>>A[i];
	cin>>S;

	vector<ll> dp(N),prefix_sum(N+1);
	prefix_sum[0]=1;
	ll ans=0;
	vector<int> before_ind(26,-1);
	rep(i,N){
		int ch_num=(S[i]-'a');
		dp[i]=prefix_sum[i];
		if(before_ind[ch_num]!=-1){
			dp[i]-=prefix_sum[before_ind[ch_num]+1];
			dp[i]+=dp[before_ind[ch_num]];
			dp[i]%=mod;
		}
		before_ind[ch_num]=i;
		prefix_sum[i+1]=(prefix_sum[i]+(dp[i]*A[i])%mod)%mod;
	}
	cout<<(mod-1+prefix_sum[N])%mod<<"\n";
	
}