IMO Shortlist 2012 problem N1
Dodao/la: arhiva3. studenoga 2013.
Call admissible a set
of integers that has the following property:
for every integer
Determine all pairs
of nonzero integers such that the only admissible set containing both
is the set of all integers.
Proposed by Warut Suksompong, Thailand
Izvor: Međunarodna matematička olimpijada, shortlist 2012