I have been given a task to find afunctionwhich satisfies:

1. Definition area for is

2. Value area for is the amount/quantity by the equivalentclass of~

3. f is injective

4. f is surjectiv

5. for all og in

What is done is actually to complete the quantity theoretical constuction of all integers from the natural numbers.

I actually have no idea where to start! Feel free to point me in a direction, all help is gratefully accepted!