N = int(input())
S = input()
ans = 0
for i in range(1, N + 1):
    for j in range(i + 1, N + 1):
        k = 2 * j - i
        if not(j < k <= N):
            continue
        if S[i - 1] == "U" and S[j - 1] == "M" and S[k - 1] == "G":
            ans += 1
print(ans)