(invert{{1,1,0,0},{2,1,0,-2},{-1,0,1,1},{-1,0,0,1}}).{{2,1,1,1},{0,4,1,3},{0,-1,2,-2},{0,-1,0,0}}.{{1,1,0,0},{2,1,0,-2},{-1,0,1,1},{-1,0,0,1}}

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