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