Interval parking functions (IPFs) are a generalization of ordinary in which each car is willing to park only fixed interval spaces. Each function can be expressed as pair (a,b), where and b dual function. We say that permutations (x,y) reachable if there an IPF (a,b) such x,y the outcomes a,b, respectively, functions. Reachability reflexive antisymmetric, but not general transitive. prove its t...