# Proving that lists are not permutations using reflection

Using the notion of permutations defined in this exercise
and the counting function defined in
this exercise.
show that if a list is a permutation of another list, then any natural number
occurs as many times in both lists.

Build a specialized reflection tactic ```NoPerm \(n\)`'' that solve goals
of the form `~perm l l'` by finding an element of the first
list that does not occur the same number of times in both lists.

## Solution

This file

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