For each valid cut set q we first determine the unlabeled connector configuration of F (q) and call it C(q). We then check for each synthon reaction R, if based on its unlabeled connector configuration L(R) could contain the cut set, i.e. if we find an injective map Ψ from the integers in C(q) to the integers in L(r), such that ∀i ∈ C(q) : Ψ(i) >= i.