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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
I agree, that string is valid, and the first non-repeating letter (meeting the challenge reqs) is
p, which means it's valid.However, that string also has several control characters (invisible in print), which are also duplicated. Those hidden characters could be confusing.
There is only one 'p' in this string?!