整理了前人一些比较有用的 Hack 并用字符画出情况，可供调试以及题意理解。

4 4 2
0 0
2 1
0 0          -> input
0 0
1 1 3
3 2 4

x | x | x
x | x x x    -> pipes
x x x | x
x | x | x
0 2 0 0      -> x_i and y_i
0 1 0 0

0            -> output
1

---------------

3 4 2
0 0
1 0
0 0
1 0 2
2 2 4

x | | x
x | x x
x | | x
x x | x
0 1 0
0 0 0

1
2

---------------

4 6 2
0 0
3 0
0 1
0 0
1 0 2
3 4 6

x | x | x
x | x x x
x | x | x
x | x | x
x | x | x
x x x | x
0 3 0 0
0 0 1 0

1
2

---------------

3 7 2
1 1
1 1
2 2
1 1 3
2 3 6

x | | x
x | | x
x | x x
x | x x
x | | x
x x | x
x | | x
1 1 2
1 1 2

1
2

---------------

7 6 4
1 1
2 2
1 3
1 3
2 2
2 2
3 1
4 3 6
6 2 6
2 3 5
5 3 6

x x | x | | | x
x x | x x x x x
x x x x x x x x
x x | x | | x x
x x | x | | | x
x x | x | | | x
1 2 1 1 2 2 3
1 2 3 3 2 2 1

0
2

---------------

5 5 3
1 2
2 1
1 1
1 2
2 2
2 1 4
1 2 4
4 2 4

x | | x | x
x | | x | x
x x x x x x
x | x x | x
x | | x | x
1 2 1 1 2
2 1 1 2 2

1
2

---------------

7 7 6
2 2
1 1
1 3
3 2
1 2
1 3
1 3
3 1 5
6 3 7
5 3 7
2 1 4
1 2 5
4 1 4

x | | | | | | x
x | | | | x x x
x | | | | x x x
x x | x | x x x
x x x x x | | x
x | x x x | | x
x | | | | | | x
2 1 1 3 1 1 1
2 1 3 2 2 3 3

1
4

---------------

5 9 3
3 2
2 1
3 4
1 2
1 1
1 3 6
2 4 7
4 4 6

x | | x | x
x | | x | x
x | | x | x
x | x x | x
x x x x x x
x x | x | x
x | | x | x
x | | x | x
x | | x | x
3 2 3 1 1
2 1 4 2 1

1
4