Comment please/ C++ in Vocareum

Recognizing error cases associated with the wrong number of file names and files that cannot be opened. Handling cases with an empty SUBSTITUTIONS file. Handling simple substitutions (no punctuation, no case changes).Note that any and all whitespace between WORDS in input is printed unchanged to output. If exactly two filenames are not provided, print TWO FILENAMES REQUIRED, and stop. If a file cannot be opened or read for any reason, print the error message BAD FILE FILENAME, and stop. It is possible that either or both of the files your program reads may be empty. It is also possible that the second file may contain no words. Neither of these situations are errors. ANd also delcares the number of changes made