Distances of groups of prime order

Given two finite groups G(.), G(*) defined on the same set G, their distance is the number of pairs (x,y) for which x.y and x*y differ. The Cayley stability of a group G(.) is the minimum distance of G(.) from another group defined on G. We show that the Cayley stability of the cyclic group of prime order p is 6p-18, for every p>7.