Szudzik's Elegant Pairing Function

http://szudzik.com/ElegantPairing.pdf

For all non-negative integers:

uncurry pair . unpair = id
unpair . uncurry pair = id

Addapted from https://gist.github.com/klntsky/7026018c3341e6aa17bc237746ee0256#file-pairing-hs We use Int rather than Integer, and need accuracy in the range [0..10000]