Prompt the user input from the keyboard (a word which may contain one or more Spaces, tabs, TAB, carriage returns, line breaks, and ends with the EOF marker, namely as input end user input Ctrl + Z), to replace the capital letters with the corresponding lower case letters, lower case letters with the corresponding capital letters. To avoid the indecent words, still need to be one of the "bullshit" (regardless of case) replaced with the "bush" (all lowercase). Finally will replace before and after the two sentences respectively displayed on the screen.