Consider the following recursive function:

def mystery$($x$,$y$)$:

if x $<0$:

return $-$ mystery$(-$x$,$ y$)$

elif y $<0$:

return $$ mystery$($x$,-$y$)$

elif x $==0$ and y $==0$:

return $0$

else:

return $100*$ mystery$($x $//10,$ y $//10)+10*($x $\%10)+$ y $\%10$

What is returned with the following method call: mystery $(5,7).$ Show your work.