提示用户从键盘输入一句话（其中可能包含空格，以EOF标记作为结束，即用户输入Ctrl+Z作为输入结束），将其中的大写字母换成对应的小写字母，小写字母换成对应的大写字母。为避免不雅字眼，还需要将其中的“bullshit”（不论大小写）替换为“bush”（全部小写）。最后将替换前后的两句话分别显示在屏幕上。-Prompts the user to input a word from the keyboard (which may contain spaces, as the end of the EOF marker, the user input as the input end of the Ctrl+ Z), which will be replaced by the corresponding lowercase uppercase letters, lowercase letters replaced by the corresponding uppercase letters. To avoid indecent words, it needs to be one of the " bullshit"　(regardless of case) with the " bush"　(all lowercase). Finally, two words will be replaced, respectively, before and after the show on the screen.