Ordering

Ordering[list] gives the positions in list at which each successive element of Sort[list] appears. 

Ordering[list,n] gives the positions in list at which the first n elements of Sort[list] appear. 

Ordering[list,-n] gives the positions of the last n elements of Sort[list]. 

Ordering[list,n,p] gives positions in list of elements of Sort[list,p]. 

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