谁帮忙解释一下这道题，一道ACM的题

[xyq1986]

specialist in VLSI design testing must decide if there are some components that cover each other for a given design. A component is represented as a rectangle. Assume that each rectangle is rectilinearly oriented (sides parallel to the x and y axis), so that the representation of a rectangle consists of its minimum and maximum x and y coordinates.

Write a program that counts the rectangles that are entirely covered by another rectangle.

The input contains the text description of several sets of rectangles. The specification of a set consists of the number of rectangles in the set and the list of rectangles given by the minimum and maximum x and y coordinates separated by white spaces, in the format:

nr_rectangles
xmin1 xmax1 ymin1 ymax1
xmin2 xmax2 ymin2 ymax2
…
xminn xmaxn yminn ymaxn

The output should be printed on the standard output. For each given input data set, print one integer number in a single line that gives the result (the number of rectangles that are covered). An example is given in Figure 1.


Input

3
100 101 100 101
0 3 0 101
20 40 10 400
4
10 20 10 20
10 20 10 20
10 20 10 20
10 20 10 20

Output

0
4
能讲解一下题意吗？

[galois_godel]

求被完全覆盖的矩形个数阿

[xyq1986]

0 3 0 101应该就是x=0,x=3,y=0,y=101所围成的矩形吗？

[galois_godel]

是阿

[xyq1986]

那我怎么老超时啊？时间限制是7s，我还超时，不知怎么回事，我的时间复杂度是O（n^2)