N = int(input())
S = input()
ans = int("BB" in S)
if S[0] != "B" or S[1] != "B":
    ans += 1
for i in range(2, N):
    if S[i] == "A":
        ans += 1
    else:
        if S[i-1] == "B":
            continue
        elif S[i-1] == "A" and S[i-2] == "B":
            continue
        ans += 1
print(ans)