import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        char[] arr = sc.next().toCharArray();
        TreeSet<Integer> uSet = new TreeSet<>();
        TreeSet<Integer> mSet = new TreeSet<>();
        TreeSet<Integer> gSet = new TreeSet<>();
        for (int i = 0; i < n; i++) {
            if (arr[i] == 'U') {
                uSet.add(i);
            } else if (arr[i] == 'M') {
                mSet.add(i);
            } else {
                gSet.add(i);
            }
        }
        long ans = 0;
        for (int m : mSet) {
            for (int u : uSet) {
                if (m < u) {
                    break;
                }
                if (gSet.contains(m * 2 - u)) {
                    ans++;
                }
            }
        }
        System.out.println(ans);
    }
}