det [[x,1,2,3,4,5,6],[1,x,1,2,3,4,5],[2,1,x,1,2,3,4],[3,2,1,x,1,2,3],[4,3,2,1,x,1,2],[5,4,3,2,1,x,1],[6,5,4,3,2,1,x]]

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