人体口腔上皮细胞常被用作动物细胞的观察材料．

                                                                                              赵孟頫过扬州
         元盛时，扬州有赵氏者，富而好客。其家有明月楼，人作春题，多未当意者。一日，赵子昂过扬，主人知之，迎致楼上，盛筵相款，所用皆银器。酒半，出纸笔求作春题。子昂援笔书云：“春风阆苑客三千，明月扬州第一楼。”主人得之，喜甚，尽撤酒器以赠。
       【注释】①元：元朝。②春题：春联。③阆苑：传说中神仙居住的地方。此为赞美明月楼。
       【文化常识】赵孟頫其人。上文说到的“赵子昂”，即元朝书画家赵孟頫，字子昂，号松雪道人。他的字圆转遒丽，世称“赵体”，与“颜体”、“柳体”等并驾齐驱。他还善于诗文、工于篆刻，是个多才多艺的文人。

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     There are many ways for us to reduce(减少) waste. For 1, we can reduce paper and plastic bags. We can also recycle newspapers, glass, and cans(易拉罐) to make new things. Here are some useful ways to 2 waste.
     Write on 3 sides of paper
     Many people write on only one side of their paper. Why not stop wasting the other side? Some students only use half the pages of their 4 before getting new ones. Try to use up all the paper. People often give cards on birthdays or festivals. How about trying to 5 e-cards instead?
     Don't throw away your old batteries.
     Maybe you do not know that old batteries make the earth 6. This is because they have poisonous parts in them. So, don't throw away batteries. 7 them together. Try to use rechargeable(充电的) batteries for your games and CD players.
     Give off all your unwanted clothes
     There are many poor families in China. You may ask your mother to 8 your unwanted clothes. Then you can pass them on to those poor children. You will feel 9 that you are helping someone else. Also, you can understand 10 your friends or relatives(亲戚) want them before throwing them away.

运行如图所示的伪代码，则输出的结果S为____ ．