I can't get AC. I used correct algoritm (it is known,
because solution with this algoritm was AC on regional
contest) with recursive formula. Then I changed recursive
formula with non recursive (thinking there problems with
floating point calculations), no effect - only WA.

Also, there was some strange compile errors (!!!) like :

12835
temp\12835(26) : error C2471: cannot update program
database 'e:\judge\vc60.pdb'