#include <iostream>
#include <map>
#include <vector>

bool is_cpctf(const std::vector<char> &v) {
    if (v[0] != v[2]) {
        return false;
    }
    
    std::map<char, int> count;
    for (char c : v) {
        count[c]++;
    }
    
    return count.size() == 4 && count[v[0]] == 2;
}

int main() {
    int N;
    std::string S;
    
    std::cin >> N >> S;
    int count = 0;
    
    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++) {
                        std::vector<char> v = {S[i], S[j], S[k], S[l], S[m]};
                        if (is_cpctf(v)) count++;
                    }
                }
            }
        }
    }
    
    std::cout << count << std::endl;
    
    return 0;
}