人啊，总是回忆着过去，想象着未来，却不知把握现在；人啊，总是在拥有时不知珍惜，失去时才追悔莫及；人啊，总是羡慕那些“走”时无法带走的利禄，让自己的人生变得酸涩辛苦；人啊，总是把复杂的东西看得简单，同时又把简单的东西搞得复杂；人啊，总是在面对浩瀚的天宇时，才会发现自己的渺小；人啊……
It is Sunday morning，Helen and her brother David are 1a walk in the park. There are lots of signs in the park. Helen knows a lot 2 them. But David 3. Suddenly Helen sees a boy climbing a tree. She says to the boy,"Don't climb the tree. Can't you see the 4Over there?" The boy jumps off the tree soon. David points to the sign and says to Helen，"So the sign means we 5climb trees，right?" "Yes." says Helen.
78−35+18−25 =____
