import sys
INF = float('inf')
#10**20,2**63,float('inf')
MOD = 10**9 + 7
MOD2 = 998244353
from collections import defaultdict
def solve():
    def II(): return int(sys.stdin.readline())
    def LI(): return list(map(int, sys.stdin.readline().split()))
    def LC(): return list(input())
    def IC(): return [int(c) for c in input()]
    def MI(): return map(int, sys.stdin.readline().split())
    N = II()
    S = input()
    Ans = 0
    BB = 0
    for i in range(N-1):
        if((S[i]=="A" and S[i+1]=="A") or (S[i]!=S[i+1])):
            Ans += 1
        elif((S[i]=="B" and S[i+1]=="B")):
            BB=1
    for i in range(N-2):
        if(S[i:i+3]=="BAB"):
            Ans-=1
    print(Ans+BB)
    return
solve()