import java.util.Scanner;

class Main {
    // U M G
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String s = sc.next();
        int ans = 0;
        for (int i = 0; i < n; i++) {
            char c = s.charAt(i);
            if (c != 'M') {
                continue;
            }
            for (int j = 0; j < i; j++) {
                char u = s.charAt(j);
                if (u != 'U') {
                    continue;
                }
                int sa = i - j;
                if (sa + i >= n) {
                    continue;
                }
                char g = s.charAt(sa + i);
                if (g == 'G') {
                    ans++;
                }

            }
        }
        System.out.println(ans);
        sc.close();
    }
}