After many years of development, Merck has finally discovered a simple model which helps with computer aided drug design. Different chemical substances are viewed as two-dimensional "puzzle" pieces which may be combined in a three-dimensional way, forming more complex structures of atoms. Special combinations of these pieces have very special chemical properties. These combinations which are known as ACM (Anachronistic Cube Molecules) result from combining six individual puzzle pieces along their edges to form a complete cube (see Figure 3).
Given six pieces, decide whether they can be put together to form a cube of dimension 6 * 6 * 6, with no holes visible from the outside. Each piece can be thought of as being cut from a plate of wood of dimension 6 * 6 * 1, with the 4 * 4 * 1 plate in the centre untouched. A piece can be used the one or the other way around, i.e., there is no distinction between the inside and the outside.