N = int(input())
S = input()
cnt = 0
for i in range(N - 2):
    for j in range(i + 1, N//2 + i//2 + 1):
        k = 2 * j - i
        if S[i] == "U" and S[j] == "M"and S[k] == "G":
            cnt += 1
print(cnt)