#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int n;
ll ans = 0;
string s;

void solve(const string &s, const string &target) {
    int m = 5;
    ll dp[6] = {};
    dp[0] = 1;
    for (int i = 0; i < s.size(); ++i) {
        for (int j = m - 1; j >= 0; --j) {
            if (s[i] == target[j]) {
                dp[j + 1] += dp[j];
            }
        }
    }
    ans += dp[m];
}
int main(){
    cin >> n >> s;
    for(char c = 'A'; c <= 'Z'; c++){
        for(char p = 'A'; p <= 'Z'; p++){
            for(char t = 'A'; t <= 'Z'; t++){
                for(char f = 'A'; f <= 'Z'; f++){
                    set<char> st = {c, p, t, f};
                    if(st.size() != 4) continue;
                    string x = "";
                    x += c;
                    x += p;
                    x += c;
                    x += t;
                    x += f;
                    solve(s, x);
                }
            }
        }
    }
    cout << ans << endl;
}