N = int(input())
S = list(input())
if N == 2:
	print(1)
	exit()

T = []
for i in range(N-1):
	if (S[i] == 'B') & (S[i+1] == 'B'):
		pass
	else:
		T.append(S[i])
if (S[-1] == 'B') & (S[-2] == 'B'):
	T.append('B')
elif S[-1] == 'A':
	T.append('A')
# print(''.join(T))
M = len(T)
X = 0
for i in range(M-2):
	if (T[i] == 'B') & (T[i+2]=='B'):
		X += 1
ans = M - X
if N == M:
 	ans -= 1
print(ans)