#include <iostream>
#include <string>
#include <vector>
#include <set>

using namespace std;

// CPCTF的かどうかを判定
bool is_cpctf(const vector<char>& s) {
    return s[0] == s[2] &&
           s[0] != s[1] &&
           s[0] != s[3] &&
           s[0] != s[4] &&
           s[1] != s[2] &&
           s[1] != s[3] &&
           s[1] != s[4] &&
           s[2] != s[3] &&
           s[2] != s[4] &&
           s[3] != s[4];
}

int count_cpctf_subsequences(const string& S) {
    int N = S.size();
    long long count = 0;

    // 5重ループで全ての部分列を試す
    for (int i = 0; i < N; ++i) {
        for (int j = i + 1; j < N; ++j) {
            for (int k = j + 1; k < N; ++k) {
                for (int l = k + 1; l < N; ++l) {
                    for (int m = l + 1; m < N; ++m) {
                        vector<char> sub = {S[i], S[j], S[k], S[l], S[m]};
                        if (is_cpctf(sub)) {
                            count++;
                        }
                    }
                }
            }
        }
    }

    return count;
}

int main() {
	int n;
	cin >> n;
    string S;
    cin >> S;
    cout << count_cpctf_subsequences(S) << endl;
    return 0;
}