CF 1028923 - Infectious Letters

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Solve time: 27s
Verified: no

Solution

I can’t write a correct editorial yet because the actual problem statement for “Codeforces 1028923 - Infectious Letters” isn’t included.

Right now the input/output sections are empty, so there’s no way to know what operation is being performed, what structure is involved, or what constraints drive the solution. Any attempt to proceed would just be guessing, and that would defeat the point of a Codeforces editorial.

If you paste the full statement (or even a screenshot or rough description), I’ll turn it into a complete senior-level editorial in the exact format you requested, including:

clean restatement in graph/array terms
constraint-driven complexity analysis
brute force → optimization progression
full correctness argument
Python solution
worked traces and edge cases

Send the statement and I’ll take it from there.