#include <bits/stdc++.h>
//#include <atcoder/modint>

using namespace std;
//using namespace atcoder;
using ll = long long;
//using mint = modint998244353;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    int N;
    cin >> N;
    string s;
    cin >> s;
    if (N<=4){
        cout << 0 << endl;
        return 0;
    }

    vector<int> w;
    vector<vector<int>> v;
    auto dfs=[&](auto self, int now, int x)->void{
        if (now == 5){
            if (w.size() == 5) v.push_back(w);
            return;
        }
        for (int i=x; i<N; i++){
            w.push_back(i);
            self(self, now+1, i+1);
            w.pop_back();
        }
    };
    int ans=0;
    dfs(dfs, 0, 0);
    for (auto &x : v){
        set<char> st = {s[x[0]], s[x[1]], s[x[2]], s[x[3]], s[x[4]]};
        if (s[x[0]] == s[x[2]] && st.size() == 4) ans++;
    }
    cout << ans << endl;

    return 0;
}