Zero maps to zero. All even numbers $n$ map to $n/2$ and all odd numbers $n$ map to $-(\frac{n-1}{2}+1).$ This map is one to one and onto and hence invertible.
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Zero maps to zero. All even numbers $n$ map to $n/2$ and all odd numbers $n$ map to $-(\frac{n-1}{2}+1).$ This map is one to one and onto and hence invertible.