Pluralize!

Given a list of words in the singular form, return a set of those words in the plural form if they appear more than once in the list.

Examples

pluralize(["cow", "pig", "cow", "cow"]) ➞ { "cows", "pig" }

pluralize(["table", "table", "table"]) ➞ { "tables" }

pluralize(["chair", "pencil", "arm"]) ➞ { "chair", "pencil", "arm" }

Notes

• This is an oversimplification of the English language so no edge cases will appear.
• Only focus on whether or not to add an s to the ends of words.
• All tests will be valid.