N = int(input())
S = str(input())
count = 0
for i in range(N-2):
  for j in range(i+1,N-1):
    if 2*j-i >= N:
      continue
    if S[i] == "U" and S[j] == "M" and S[2*j-i] == "G":
      count += 1
print(count)