N = int(input())
S = input()

ans = 0
K = (N-1) // 2
for delta in range(1,K+1):
    for i in range(N):
        if i + delta * 2 >= N:
            break
        if S[i] == 'U' and S[i+delta] == 'M' and S[i + 2 * delta] == 'G':
            ans += 1
print(ans)