I just saw that my rating was reduced and i have been charged for plagiarism in July Cook Off divisi

I just saw that my rating was reduced and i have been charged for plagiarism in July starter 97. Though i had solved it completely on my own & was in no manner involved in any kind of cheating from any source.
I haven’t even received a mail regarding this
So, i want to know why was i charged for plagiarism even though the code is my own & what i need to do about this as its a wrong charge ?

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