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

cnt = 0
for i in range(n):
    if s[i] == "U":
        for j in range(i, n):
            if s[j] == "M":
                for k in range(j, n):
                    if s[k] == "G":
                        if j - i == k - j:
                            cnt += 1

print(cnt)