Hãy nhin số 6 trong năm giây (không tính số ở đề bài)
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
9999999999999999999999999999999999999999999999999999999999
toàn 9 chữ có 6 đâu
lộn ngược lại là có số 6