**①A****ttention to the big numbers**

Let's start with the same number as the number of squares or where there is only one pattern.

In the example, it is 10 for 10 squares, so you can paint one horizontal row first.

Next, apply 8 squares on top of it, leave 1 square open, and paint 1 square to use 10 squares, so this method of painting is possible.

**②****Find a place where you can absolutely paint**

In the example, 7 squares from the top and 7 squares from the bottom are counted.

The overlapping part (green frame) is the part that is always painted.

**③Use the painted square as a hint to continue painting.**

In the example, by applying it to the vertical to some extent, the 4 squares on the side are possible, and the space before and after that is blank. The blank is a hint, and you can paint 6 vertical squares.

④Add ✕ to squares that can never be painted

As you proceed, you will find the squares that can never be painted. In the example, 3 out of the possibility of painting 4 squares is confirmed, so blanks are confirmed before and after 1 square is opened.

By hitting ✕ first, it will lead to hints later.

⑤ Attention to the square near the wall

If there is a painted square near the edge, it is a chance to paint.

In the example, you can surely paint 2 squares regardless of whether you paint 4 squares from the leftmost square or 4 squares from the painted square.

By repeating ① to ⑤, we will separate the areas where it can be applied reliably and the areas where it cannot be applied reliably.

There are other strategies, but I think the problems on this site can be solved by the strategies so far.

good luck!!!!

*Last Update 2021/8/27*