It's possible if and only if n=1 or n is even
Source:
September 20, 2010
geometry3D geometrycombinatoricspackingIMO Shortlist
Problem Statement
Prove that it is possible to place parallelepipedic (rectangular) pieces of soap of dimensions in a cubic box with edge if and only if is even or .Remark. It is assumed that the edges of the pieces of soap are parallel to the edges of the box.