def main():
    length = int(input())
    strings = input()

    if length == 2:
        print(1)
        return

    BB_found = False
    counter = 0
    current_idx = 0
    while current_idx < length-1:
        a_idx = strings.find("A", current_idx)
        if a_idx == 0:
            counter += 1
            current_idx = 1
            continue

        if a_idx == length - 1:
            if strings[a_idx-1] == "B":
                counter += 1
                break

        if a_idx != -1:
            previous_2letters = strings[a_idx-1:a_idx+1]
            if previous_2letters == "AA":
                counter += 1
            else:
                if strings[a_idx+1] == "A":
                    counter += 2
                else:
                    counter += 1

            diff = a_idx - current_idx
            if diff >= 2:
                BB_found = True
            current_idx = a_idx + 1
        else:
            BB_found = True
            break

    if BB_found:
        counter += 1
    print(counter)


if __name__ == "__main__":
    main()