The following changes have been made to the problem:
- The checking program strictly checks that the initial formatting is preserved, for example it rejects outputs with additional empty lines before or after the text.
- Missing limitations added to the problem statements:
    - The words in the text to correct are no longer than 16 characters.
    - The lines in the text to correct are no longer than 80 characters.
    - The cumulative length of all lines doesn't exceed 10000 characters.
- New tests have been added.
- Time limit has been reduced to 0.5 sec.
- All solutions have been rejudged. 44% of authors have lost their accepted solutions.