n = int(input())
s = input()
ans = 0
for j in range(1, n - 1):
    if s[j] == 'M':
        t = min(j, n - j)
        for i in range(1, t + 1):
            if s[j - i] == 'U' and s[j + i] == 'G':
                ans += 1
print(ans)