số 8 ở đâu trong ma trận số này?
999999999999999999999999999999999999
999999999999999999999999999999999999
999999999999999999999999999999999999
999999999999999999999999999999999999
999999999999999899999999999999999999
999999999999999999999999999999999999
999999999999999999999999999999999999
999999999999999999999999999999999999
999999999999999999999999999999999999
ở giữa
ở hàng thứ 5