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

int main() {
	int N, ans = 0;
	string S;

	cin >> N;
	cin >> S;
	for (int i = 0;i < N;i++) {
		for (int j = 1;j <= (N - i-1) / 2;j++) {
			if (S[i] == 'U' && S[i + j] == 'M' && S[i + 2 * j] == 'G') {
				ans++;
			}
		}
	}
	cout << ans;
}