#include <iostream>
using namespace std;
int main(void) {
	int n;
	string s;
	cin >> n >> s;
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		if (s[i] == 'U') {
			for (int j = i + 1; j < n; ++j) {
				if (s[j] == 'M' && j + (j - i) < n) {
					if (s[j + (j - i)] == 'G')
						++ans;
				}
			}
		}
	}
	cout << ans << endl;
	return 0;
}