Editorial for COCI '15 Contest 4 #3 Deathstar

Remember to use this editorial only when stuck, and not to copy-paste code from it. Please be respectful to the problem author and editorialist.
Submitting an official solution before solving the problem yourself is a bannable offence.

It is necessary to notice that the construction $a_i =$ $a_{i} =$ bitwise or of all $m_{ij}$ $m_{i j}$ for each $j$ $j$ is sufficient to meet all the requirements from the matrix. The proof of this fact is left as an exercise to the reader.

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