Unexpected error related to challenges

[Papermars]

when taking challenges and i had failed the test, after I deleted my original code, then open it again.
every time it would show the error message and I can't re-take the challenge.

the website would be https://onecompiler.com/challenges/3w8xvfbtb/strings-challenge.
don't know whether the above is enough.

comment if you need more

warm regards.

[Papermars]

https://onecompiler.com/users/42wn9kz87
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