#include <iostream>

using namespace std;

int main() {
    int dna_lenght;
    string dna;

    cin >> dna_lenght;
    cin >> dna;

    int talalt = 0;

    for (int i = 0; i < dna_lenght; i++) {
        if (dna[i] == 'A') {
            for (int j = i+1; j < dna_lenght; j++) {
                if (dna[j] == 'G') {
                    for (int h = j+1; h < dna_lenght; h++) {
                        if (dna[h] == 'T') {
                            talalt++;
                        }
                    }
                }
            }
        }
    }

    if (talalt == 0) {
        cout << talalt;
    } else {
        cout << talalt - 1;
    }


}