import java.util.*;

public class Main {
    static TreeSet<Integer> primes;
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		char[] arr = sc.next().toCharArray();
		int count = 0;
		for (int i = 0; i < n; i++) {
		    if (arr[i] != 'U') {
		        continue;
		    }
		    for (int j = 1; i + j * 2 < n; j++) {
		        if (arr[i + j] == 'M' && arr[i + j * 2] == 'G') {
		            count++;
		        }
		    }
		    
		}
		System.out.println(count);
	}
}