A (1,1)-Skolem graceful labeling of G is a Skolem graceful labeling. A
Skolem graceful labeling of nK2 gives the Skolem sequence, a (2,1)-Skolem
graceful labeling of nK2 gives the Langford sequence L(2, n) and a (k, 1)-
Skolem graceful labeling of nK2 gives a perfect sequence.