N = int(input().strip())
S = input().strip()

cnt = 0

for i in range(N-2):
  if S[i] == 'U':
    cnt += len([j for j in range(1, (N-i) // 2 + 1) if S[j+i] == 'M' and S[j*2+i] == 'G'])

print(cnt)