| has gloss | eng: In the mathematical subject of topology, Kuratowskis closure-complement problem is the question how many distinct sets can be obtained by repeatedly applying the set operations of closure and complement to a given starting subset of a topological space. The answer is: no more than 14. This result was first published by Kazimierz Kuratowski in 1922. It follows easily from the following facts that hold for any subsets S of a space, writing S^ for the closure of S, So for the interior of S, and S for its complement: |