N = int(input())
S = input()
zero = 0
one = set()
two = set()

for i in range(N-1):
	if S[i:i+2] == "AA":
		two.add(i)
	elif S[i:i+2] == "BA":
		one.add(i+1)
	elif S[i:i+2] == "AB":
		one.add(i)
	else:
		zero = 1

print(len(one)+len(two)+zero)