n = int(input())
s = list(input())
ans = 0
flg = 0
h = ["AA","AB","BA"]
for i in range(n-1):
    ss = s[i] + s[i+1]
    if ss in h: ans += 1
    if ss == "BB":flg = 1
for i in range(n-2):
    ss = s[i] + s[i+1] + s[i+2]
    if ss == "BAB":ans -= 1
print(ans+flg)