Paint the town red!

Logic Level 2

You paint the 5×55 \times 5 grid red, one square at a time. You can only paint a square red if it shares an edge with 1 or 3 blue squares (diagonals don't count).

If you continue until there is no more blue square left to be painted red according to the rule above, what's the minimum possible number of squares you can color?

Below right is an example of a sequence of how you might paint the first 4 squares.

Clarification: The square colored red with sequence number 3 now borders two blue squares, but it was bordering three blue squares at the time of coloring.


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