trời ơi 1000

if tags have number at the end, their link auto add character a at the end, so it not working. Why? How can i fix it ? Example: http://www.kilobooks.com/tags/cac-bai-toan-giai-thi-hoc-sinh-gioi-lop-3-a/ http://www.kilobooks.com/tags/cac-de-thi-hsg-lop-3-a/