tìm điểm khác biệt
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hàng ngang thứ 9 và 20 có chữ o và ở dòng cuối có ít hơn các dòng
ở hàng 9 và 20 có chữ o( tính theo hàng ngang)
Ở dòng thứ 9 từ trên xuống, có chữ o.
