Anyway, I walked a bit further and saw other people either up trees or preparing to go up trees, and then I noticed a man standing23 there directing them, a sort of foreman, and began to wonder what on earth was going on, and then on the ground I saw there were all these polythene buckets and they were full of pine cones24 and of course what they were doing was collecting pine cones, and I thought, 'Well, how tidy of them to collect pine cones to stop the ruins being, um, made, um, made untidy with all these things.' 

这个段落来自listen to this

请问最后一个句子意思和of的使用

我在查阅字典中看到另外句子双语 Remain clean and tidy of the apartment and clear living garbage on time. 保持寝室内卫生整洁，及时清理生活垃圾。

这句也是tidy后面加of，

请指教