n = int(input())
S = list(input())

ans = 0
for dif in range(1, n):
    for i in range(n):
        if i + 2 * dif >= n:
            break
        if S[i] == 'U' and S[i + dif] == 'M' and S[i + 2 * dif] == 'G':
            ans += 1
print(ans)