n = int(input())
s = input()
ans = 0
for i in range(n - 2):
    if s[i] == 'U':
        try:
            for k in range(1, (n - i) // 2 + 1):
                if s[i + k] == 'M' and s[i + k * 2] == 'G':
                    ans += 1
        except:
            err = 1
print(ans)