Strong closure of a graph

Strong closure of a graph --- сильное замыкание графа.

The strong closure of a graph [math]\displaystyle{ G }[/math] is the graph obtained from [math]\displaystyle{ G }[/math] by recursively joining pairs of nonadjacent vertices, whose degree sum is at least [math]\displaystyle{ n + 1 }[/math] ([math]\displaystyle{ n }[/math] is the number of vertices of [math]\displaystyle{ G }[/math]), until no such pair remains. The strong closure of [math]\displaystyle{ G }[/math] is denoted by [math]\displaystyle{ sc(G) }[/math]. The notion of a strong closure is useful in the study of Hamiltonian graphs.