A.p+[i*n+j-1]*k B.p+[(i-1)*n+j-1]*k C.p+[(j-1)*n+i-1]*k D.p+[j*n+i-1]*k
A.head(tail(tail(L)))B.tail(head(head(tail(L))))C.head(tail(tail(head(L))))D.head(tail(tail(tail(L))))