This is a simple arithmetic water column problem, but I didn't learn it until I was a freshman. It's a little difficult for you, but it's very simple for you. The first line has 0 shadow boxes, which is 1 less than the number of lines, the second line has 1 shadow boxes, and the third line has 2 shadow boxes, which is also 1 less than the number of lines. Of course, the fourth row must be 3. For Bush's shadow, the first line is 1, the second line is 2, the third line is 3, and the third line is 100.

If the total number of squares is calculated, the result is 199, which is actually = number of shadows+number of squares that are not shadows, right, but it can be calculated by series method.

In short, line 100 has 99 shaded boxes.