Tìm một số trong dãy số9
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999699999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
hàng số năm ở giữa và ĐỪNG ĐĂNG CÂU HỎI LINH TINH
số 6 à?