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 = input()

st = set()
x = 0
for i in range(N-1):
    if S[i] == S[i+1] == 'A':
        st.add((i, i+1))
    elif S[i] == "A":
        st.add((i))
    elif S[i+1] == 'A':
        st.add((i+1))
    else:
        x = 1

print(len(st) + x)