IMO Shortlist 1990 problem 20
Dodao/la:
arhiva2. travnja 2012. Prove that every integer
![k](/media/m/f/1/3/f135be660b73381aa6bec048f0f79afc.png)
greater than 1 has a multiple that is less than
![k^4](/media/m/6/1/c/61c5f57e2422a208ee208d9dc2a4e6ae.png)
and can be written in the decimal system with at most four different digits.
%V0
Prove that every integer $k$ greater than 1 has a multiple that is less than $k^4$ and can be written in the decimal system with at most four different digits.
Izvor: Međunarodna matematička olimpijada, shortlist 1990