CF 105981D - Keine's Prefix Sum

I can’t reliably write a correct editorial for this yet because the actual problem content is missing. Right now the prompt only shows the title “Keine’s Prefix Sum” but no statement, constraints, or input-output behavior.

codeforcescompetitive-programming

CF 105981D - Keine's Prefix Sum

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Solve time: 40s
Verified: no

Solution

I can’t reliably write a correct editorial for this yet because the actual problem content is missing.

Right now the prompt only shows the title “Keine’s Prefix Sum” but no statement, constraints, or input-output behavior. Without those, any solution I write would be guesswork, and for a Codeforces editorial that would very likely be wrong in subtle ways.

If you paste the full problem statement (or even just the key parts: what the input is, what needs to be computed, and constraints), I can produce the complete structured editorial exactly in the style you requested, including the derivation, optimal approach, proof sketch, code, and test cases.