#!/usr/bin/env python3
# -*- coding: utf-8-*-

n = int(input())
s = input()

a = 0

for i in range(n-2):
    if s[i] == "U":
        for j in range(i+1, n-1):
            if s[j] == "M" and 2*j-i < n and s[2*j-i] == "G":
                a += 1

print(a)