Xor profit problem

#1

in this problem if we consider inputs as 8 & 20 then max xor possible is 31 by considering (11 & 20) and also (15 & 16),what values should we print in solution

#2

generally just the max value is asked

but if required the condition would be given to print which one
or the question might demand all pairs
here as of the hackerblock q just the max xor profit is asked