#include <iostream>
#include <set>
#include <map>
#include <vector>
using namespace std;
const int INF = 2e9;
const int MOD = 1e9 + 7;

int main() {
    ios_base::sync_with_stdio(false);

    int n;
    cin >> n;

    string s;
    cin >> s;

    vector<int> pos;
    map<char, int> cnt;
    int k = 0;
    for(int i = 0; i < n; i++) {
        if(cnt.find(s[i]) == cnt.end()) {
            cnt[s[i]] = k;
            ++k;
        }
        pos.push_back(cnt[s[i]]);
    }

    vector<int> at(k, 0);
    map<vector<int>, int> mapa;
    int res = 0;
    for(int i = 0; i < n; i++) {
        mapa[at]++;
        at[pos[i]]++;

        int min_value = INF;
        for(int j = 0; j < k; j++) {
            min_value = min(min_value, at[j]);
        }

        for(int j = 0; j < k; j++) {
            at[j] -= min_value;
        }

        res += mapa[at];
        res %= MOD;
    }

    cout << res << endl;
    return 0;
}