> 10
> 0 0 1000 1000
> 0 0 1001 999
> 999.00
> 0 0 1000 1000
> 0 0 1000 999
> 0.00
> 0 0 1 1
> 1 1 2 2
> 0.00
> 0 0 1 1
> 1 1 2 2
> 0.00
> 1 1 2 2
> 1 1 2 2
> 0.00
> 1 1 1 1
> 0 0 4 4
> 0.00
> 
> 
> 
> The problem is not to slove how much water the board can contain,but the rainwater drop perpendicularly!!!
> 
> It do matter that rain can't drop into the "angle of the two boards" when one lineseg is over the other one ,for example,
> have a look at :
> 0 0 2 2
> 0 0 1 0.9
> No rain drop into !!!