#include <bits/stdc++.h>
#define mod 1000000007
using namespace std;
string s;
map < vector <int>, int > mp;
vector <int> val(150, -1);
vector <int> v;

int main()
{
    int n,i,j,rez = 0,k = 0;
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    cin.get();
    cin >> s;
    for(const auto &x : s){
        if(val[x] == -1) val[x] = k++;
    }
    v.assign(k, 0);
    mp[vector <int> (k, 0)] = 1;
    for(const auto &x : s){
        v[val[x]]++;
        int m = 1e9;
        for(auto &x2 : v) m = min(m, x2);
        for(auto &x2 : v) x2 -= m;
        mp[v]++;
    }
    for(const auto &x : mp) rez = (rez + (1LL * x.second * (x.second - 1) / 2)) % mod;
    cout << rez;
    return 0;
}