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