If
M
^{2}
(
i
,
j
) = 1, then there is a path of length < = 2 (a path traversing at most 2 edges) from vertex
i
to vertex
j
in the graph
G
. Alternatively, if
M
^{2}
(
i
,
j
) = 0, then there is no such path. Now generalize from here...