#include<bits/stdc++.h>
using namespace std;

int main() {
    int n = 0;
    cin >> n;
    string str = "";
    cin >> str;
    int result = 0;
    int a = 0;
    int na_ug_elott = 0;  // utoljara latott G elotti A betuk szama
    for(int i = 0; i < n; i++) {
    if(str[i] == 'A') {
        a++;
    }
    if(str[i] == 'G') {
        na_ug_elott = a;
    }
    if(str[i] == 'T') {
        result += na_ug_elott;
    }
    }
    cout << result;
}