If it's n squared, use induction! Let's start with the simplest rectangle consisting of two squares. At this time, N=2, it can be broken once, and the number of broken times =N- 1. Suppose there are three small squares now, you can break them twice, or N- 1

Suppose it's four dollars now. . . You interrupted three times. . . . . And so on. . . . To sum up, if it is to be divided into n blocks, it must be divided into N- 1 blocks. . . .

Then the difficulty increases. There are not only four pieces in the horizontal direction, but also two rows, that is, a rectangle with four pieces long and two pieces wide. I will arrange the door into two four-piece pieces first, and then each piece needs to be broken three times, so it will always be ***7 times! Or N- 1. . .

To sum it up. . . .

In fact, draw a picture first, and then add a few pictures, and you will understand. . . It's simple. . . You can understand this English, at least you are above high school. . . This math is at most elementary school olympiad. .