import sys, math
sys.setrecursionlimit(1000000)
INF = 1 << 100
#mod = 1000000007
mod = 998244353
input = lambda: sys.stdin.readline().rstrip()
li = lambda: list(map(int, input().split()))

N = int(input())
S = list(input())
ans = N-1

for i in range(1, N-1):
    if S[i-1] == S[i+1] == 'B' and S[i] == 'A':
        ans -= 1

flg = 0
for i in range(N-1):
    if S[i] == S[i+1] == 'B':
        ans -= 1
        flg = 1

print(ans + flg)