N = int(raw_input())
S = raw_input()
cnt = 0
for i in range(1, N+1):
	for j in range(i+1, N+1):
		k = 2*j-i
		if j < k:
			if S[i] == 'U' and S[j] == 'M' and S[k] == 'G':
				cnt += 1
print cnt