mat( ( -1, 0, 0, 1, 0, 0),
     (  2,-1, 0, 0, 0, 0),
     (  0, 1,-5, 0,-1, 0),
     (  0, 0, 3,-1, 0, 0),
     (  0, 1, 2, 0, 1,-1),
     (  0,-1, 0,-1, 0, 1),
     (  0, 1, 0, 1, 0,-1),
     (  0, 0, 0, 0, 0, 0),
     ( -1, 0, 0, 0, 0, 0),
     (  0, 0, 0, 0, 1, 0),
     (  0, 0, 0, 0,-1, 0 ) )