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Can anyone hack this solution or prove it correct?
By -Cap1taL-, history, 11 months ago, In English

https://codeforces.me/contest/1175/submission/238928196 For judging whether an array of length n is a 1~n permutation, I judged its sum{i^1} sum{i^2} sum{i^3} sum{i^4} and passed. Can anyone hack this solution or prove it correct? please help me :(

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11 months ago, # |
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It's incorrect.

Try this:

Spoiler

Maybe it will be difficult to construct a counterexample if you compute powers up to like $$$100$$$ and do some hashing.

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