#include <iostream>

using namespace std;

int main()
{
    int n, an = 0, ae = 0, ans = 0;
    cin >> n;
    char c;
    for(int i = 0; i < n; i++)
    {
        cin >> c;
        if(c == 'A')
        {
            an++;
        }
        else if(c == 'G')
        {
            ae = an;
        }
        else if(c == 'T')
        {
            ans+=ae;
        }
    }
    cout << ans;
    return 0;
}