// Source: https://usaco.guide/general/io

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


int main() {
	int n;
	cin>>n;
	string s;
	cin>>s;
	vector<int> a;
	for(int i=0;i<n;i++){
		if(s[i]=='A'){
			a.push_back(1);
		}
		if(s[i]=='G'){
			a.push_back(2);
		}
		if(s[i]=='T'){
			a.push_back(3);
		}
	}
	vector<int> legkozelebbig;
	n=a.size();
	int elozog=0;
	for(int i=0;i<n;i++){
		if(a[i]==2){
			for(int j=elozog;j<i;j++){
				legkozelebbig.push_back(i);
			}
			elozog=i;
		}
	}
	for(int i=elozog;i<n;i++){
		legkozelebbig.push_back(-1);
	}
	vector<int> hanydarabtvan;
	int eddigi=0;
	reverse(a.begin(), a.end());
	for(int i=0;i<n;i++){
		if(a[i]==3){
			eddigi++;
		}
		hanydarabtvan.push_back(eddigi);
	}
	reverse(a.begin(), a.end());
	int valasz=0;
	reverse(hanydarabtvan.begin(), hanydarabtvan.end());
	for(int i=0;i<n;i++){
		if(a[i]==1){
			valasz+=hanydarabtvan[legkozelebbig[i]];
		}
	}
	cout<<valasz<<'\n';
}