def main():
    n = int(input())
    s = input()

    ans = 0
    if "BB" in s:  # BBは最初の一回だけ数える
        ans += 1

    # BAB = (BA)B, B(AB) 
    # どちらも変換後はBBBになる
    s = "C" + s
    for i in range(n):
        ss = s[i:i + 2]
        if ss in ("AA", "BA"):
            ans += 1
        elif ss == "AB" and s[i - 1] != "B":
            ans += 1
    print(ans)


if __name__ == "__main__":
    main()