# -*- coding: utf-8 -*-

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

ans = 0

for i in range(n):
    for j in range(i+1,n):
        k = j + j - i
        if k >= n:
            break
        if s[i] == "U" and s[j] == "M" and s[k] == "G":
            ans += 1

print(ans)