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

lst = []

n = 1
while True:
  if n*2 >= N:
    break
  
  lst.append([n, n*2])
  
  n += 1

cnt = 0

for i in range(N-2):
  if S[i] != 'U':
    continue
  
  for j in lst:
    if j[1] + i >= N:
      break
    
    if S[j[0]+i] == 'M':
      if S[j[1]+i] == 'G':
        cnt += 1

print(cnt)