There is a snail that wants to climb a tree with a height of 12.5 meters. It can climb 4.5 meters every day during the day and slide down 3.5 meters at night. How many days does it take for this snail to climb to the top of the tree?
有一只蜗牛要爬到高12.5米的树上，它白天每天能爬上4.5米，晚上有滑下3.5米，这只蜗牛在第几天才能够爬上树顶？
<result>9</result>