 Solution

In the vertex form of Menger's theorem, for distinct nonadjacent vertices $s,t$ of a finite graph, the maximum number of pairwise internally vertex-disjoint $s$–$t$ paths equals the minimum size of an $s$–$t$ vertex separator. A separator is a subset of vertices other than $s,t$ whose deletion leaves no $s$–$t$ path; internally disjoint paths may share their endpoints but no other vertices. Equivalently, between disjoint vertex sets the maximum number of mutually vertex-disjoint connecting paths equals the minimum size of a separating vertex set, where endpoints may be deleted in that set version.