n = int(input())
s = input()
ans = 0
for j in range(n):
    if s[j] == "M":
        i = j - 1
        k = j + 1
        while 0 <= i and k <= n-1:
            if s[i] == "U" and s[k] == "G":
                ans += 1
            i -= 1
            k += 1
print(ans)