N = int(input())
S = list(input())
# N = len(S)
ans = N - 1
if N == 2:
	print(1)
	exit()
for i in range(N-2):
	if (S[i] == 'B') & (S[i+2]=='B'):
		ans -= 1
X = 0
for i in range(N-1):
	if (S[i] == 'B') & (S[i+1] == 'B'):
		X += 1
if X > 1:
	ans -= X - 1
print(ans)