#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main() {
	string dna;
	int len, ans = 0;
	cin >> len >> dna;
	int a = 0, ag = 0;
	for (char c : dna) {
		if (c == 'A') a++;
		else if (c == 'G') {
			ag += a;
			a = 0;
		}
		else if (c == 'T') {
			ans += ag;
		}
	}
	cout << ans;
}