Preprocessing of one of the languages designed for equipment management consists of the following steps:

1. Deleting empty lines. A line is considered empty if it contains only whitespace characters.
2. Concatenating lines with a line break character at the end. The line break character is the dollar sign $, which can be followed by any number of whitespace characters. Concatenating is performed as follows: characters starting with the dollar sign and followed by whitespace characters to the end of the line (including the line feed itself) are excluded from the character stream.
3. Deleting lines with comments. The language has only one-line comments. Comment lines start with a double dollar sign: $$, followed by at least one non-whitespace character. From the beginning of the line to the double dollar sign $$, only whitespace characters are allowed – the presence of other characters in front of it means that this is not a comment. The comment continues to the end of the line, and cannot be moved to the next one using the line break character. The entire comment line is deleted, including the leading whitespace characters (if any).

Spaces (code 32) and tabs (code 9) are considered whitespace characters in the language.

The program always ends with an empty line.

The conversions are carried out in the specified order:

• The first point applies to the entire input stream – after it, there are no empty lines left in the stream.
• The second point applies to all lines of the stream, taking into account that the initial line involved in the concatenating cannot be a comment.
• For the resulting stream, the third point is executed.

Write a program that performs preprocessing of the described type.