  ***   at top-level: Mat([1])+matrix(0,1)
  ***                         ^------------
  *** _+_: impossible addition t_MAT + t_MAT.
  ***   at top-level: 1/matrix(2,2,i,j,Mod(
  ***                  ^--------------------
  *** _/_: non invertible matrix in gauss
Total time spent: 4
