#include <bits/stdc++.h>
using namespace std;
constexpr int Inf = 1000000010;
constexpr long long INF = 2000000000000000010;
template <typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true;} return false;}
template <typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true;} return false;}

template <typename T, typename U>
T modpow(T N, U P, T M = -1) {
    if (P < 0) return 1;
    T ret = 1;
    if (M != -1) ret %= M;
    while (P) {
        if (P & 1) {
            if (M == -1) ret *= N;
            else ret = ret * N % M;
        }
        P /= 2;
        if (M == -1) N *= N;
        else N = N * N % M;
    }
    return ret;
}

constexpr long long MOD = 998244353;

int main() {
    int n;
    string s;
    cin >> n >> s;
    int ret = 0;
    for(int a = 0;a < n;a++) {
        for(int b = a + 1;b < n;b++) {
            for(int c = b + 1;c < n;c++) {
                for(int d = c + 1;d < n;d++) {
                    for(int e = d + 1;e < n;e++) {
                        if(s[a] == s[c] && s[a] != s[b] && s[a] != s[d] && s[a] != s[e] && s[b] != s[d] && s[b] != s[e] && s[d] != s[e]) ret++;
                    }
                }
            }
        }
    }
    cout << ret << endl;
}