Computer Programming Contest Preparation

    1 20
    2 3 6 -1
    3 5 3 5
    4 6 2 9
    5 1 2 7
    6 0 9 3
    7 6 0 6
    8 2 6 1
    9 8 7 9
   10 2 0 2
   11 3 7 5
   12 9 2 2
   13 8 9 7
   14 3 6 1
   15 2 9 3
   16 1 9 4
   17 7 8 4
   18 5 0 3
   19 6 1 0
   20 6 3 2
   21 0 6 1
   22