1583：Choose Your Words Carefully

Let's face it, most students who do a good job on programming contest problems aren't the best writers. However, there is no artistic process that a good programmer can't improve with a little program to automate the process.
In this case, your writing problem is a tendency to use words too often. To help check for this,you are going to write a program that will search your papers for the word or words you use most often.

The input consists entirely of your paper. Each line will be under 80 characters and will contain words, punctuation, and numbers. Words consist of the characters {a-z,A-Z,0-9}. Words are separated by whitespace, end-of-line, and punctuation. The punctuation that may be found includes the characters

,.;\'`\"()/:-

.No other characters will be found in the input.
The input ends at end-of-file.
Word comparisons are case-insensitive.

Your output begins with the line:
< n > occurrences
where n is the number of times the most frequently appearing word occurs.
Following that line will be the words that occurred n times, one per line. The words must be listed in alphabetic order.