#P3465. Life is a Line

    ID: 2349 远端评测题 1000ms 64MiB 尝试: 0 已通过: 0 难度: (无) 上传者: 标签>2010 ACM-ICPC Multi-University Training Contest(3)——Host by WHU

Life is a Line

Problem Description

There is a saying: Life is like a line, some people are your parallel lines, while others are destined to meet you.
Maybe have met, maybe just a matter of time, two unparallel lines will always meet in some places, and now a lot of life (i.e. line) are in the same coordinate system, in a given open interval, how many pairs can meet each other?

Input

There are several test cases in the input.

Each test case begin with one integer N (1 ≤ N ≤ 50000), indicating the number of different lines.
Then two floating numbers L, R follow (-10000.00 ≤ L < R ≤ 10000.00), indicating the interval (L, R).
Then N lines follow, each line contains four floating numbers x1, y1, x2, y2 (-10000.00 ≤ x1, y1, x2, y2 ≤ 10000.00), indicating two different points on the line. You can assume no two lines are the same one.

The input terminates by end of file marker.

Output

For each test case, output one integer, indicating pairs of intersected lines in the open interval, i.e. their intersection point’s x-axis is in (l, r).

3 0.0 1.0 0.0 0.0 1.0 1.0 0.0 2.0 1.0 2.0 0.0 2.5 2.5 0.0
1

Author

iSea @ WHU