N = int(input())
S = input()
ans = 0

for i in range(N):
    if S[i] == "U":
        for j in range(i + 1, N):
            if S[j] == "M":
                if j + j - i < N:
                    if S[j + j - i] == "G":
                        ans += 1

print(ans)