mat( ( 1,-1, 0,-1, 0, 1, 0,0,0,0, 0, 0, 0),
     ( 0, 0, 0, 1,-1, 0, 0,0,0,0, 0, 0, 0),
     ( 0, 0, 0, 0, 1,-1,-1,0,0,0, 0, 0, 0),
     ( 0, 0,-1, 0, 0, 0, 1,0,0,0, 0, 0, 0),
     ( 0, 0, 0, 0, 0, 0, 0,1,0,0,-1, 0, 0),
     ( 0, 0, 0, 0, 0, 0, 0,0,1,0, 0,-1, 0),
     ( 0, 0, 0, 0, 0, 0, 0,0,0,1, 0, 0,-1),
     ( 0, 0, 1, 0, 0, 0, 0,0,0,0, 0, 0, 0 ) )