
ZOJ Problem Set  3273
Description Ted has a new house with a huge window. In this big summer, Ted decides to decorate the window with some posters to prevent the glare outside. All things that Ted can find are rectangle posters. However, Ted is such a picky guy that in every poster he finds something ugly. So before he pastes a poster on the window, he cuts a rectangular hole on that poster to remove the ugly part. Ted is also a careless guy so that some of the pasted posters may overlap when he pastes them on the window. Ted wants to know the total area of the window covered by posters. Now it is your job to figure it out. To make your job easier, we assume that the window is a rectangle located in a rectangular coordinate system. The window's bottomleft corner is at position (0, 0) and topright corner is at position (50000, 50000). The edges of the window, the edges of the posters and the edges of the holes on the posters are all parallel with the coordinate axes. Input The input contains several test cases. For each test case, the first line contains a single integer N (0<N<=50000), representing the total number of posters. Each of the following N lines contains 8 integers x1, y1, x2, y2, x3, y3, x4, y4, showing details about one poster. (x1, y1) is the coordinates of the poster's bottomleft corner, and (x2, y2) is the coordinates of the poster's topright corner. (x3, y3) is the coordinates of the hole's bottomleft corner, while (x4, y4) is the coordinates of the hole's topright corner. It is guaranteed that 0<=xi, yi<=50000(i=1...4) and x1<=x3<x4<=x2, y1<=y3<y4<=y2. The input ends with a line of single zero. Output For each test case, output a single line with the total area of window covered by posters. Sample Input 2 0 0 10 10 1 1 9 9 2 2 8 8 3 3 7 7 0 Sample Output 56 Source: Asia 2009, Ningbo (Mainland China) 