#include <iostream>
#include <string>

std::string beolvas(std::istream &be) {
    int n;
    std::string dns;
    
    be >> n >> dns;

    return dns;
}

void feldolgoz(const std::string &dns) {
    const auto n = static_cast<int>(dns.size());

    int a_db = 0, ag_db = 0, agt_db = 0;
    for (int i = 0; i < n; i++) {
        switch (dns[i]) {
        case 'A':
            a_db++;
            break;

        case 'G':
            ag_db = a_db;
            break;

        case 'T':
            agt_db += ag_db;
            break;
        }
    }

    std::cout << agt_db << '\n';
}

int main() {
    const auto dns = beolvas(std::cin);
    feldolgoz(dns);

    return 0;
}