[ [ 1,-1,0, 0, 0,0, 0, 0 ],
  [ 0, 2,1,-1, 0,0, 0, 0 ],
  [ 0, 0,0, 2,-1,0, 0, 0 ],
  [ 0, 0,0, 0, 0,1,-1, 0 ],
  [ 0, 0,0, 0, 0,0, 2,-1 ] ]