Computer Programming Contest Preparation

    1 5   2
    2 4
    3 3
    4 2 1 
    5 1 
    6 0 1 2 3 4 5
    7 
    8 
    9 p1 = (1,2)
   10 p2 = (2,5)
   11 
   12 p1 x p2 = det( x1 x2 )
   13              ( y1 y2 )
   14         = x1*y2 - x2*y1
   15         = -p2 x p1
   16 
   17 p1 x p2
   18  ( 1 1 )
   19  ( 2 3 )
   20  (1 * 5) - (2 * 2)
   21  5 - 4
   22  1
   23 
   24  - (p2 x p1)
   25   - ( (2 * 2) - (1 * 5))
   26   - (4 - 5)
   27   - (-1)
   28   1