import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
n = ii()
s = input()

ans = 0
t = False
for i in range(n - 1):
    if s[i] + s[i + 1] == 'BB':
        t = True
    elif i < n - 2 and s[i] + s[i + 1] + s[i + 2] == 'BAB':
        pass
    else:
        ans += 1
print(ans + t)