X ( 1 , 4 , 2 , 5 ) X ( 3 , 9 , 4 , 8 ) X ( 5 , 10 , 6 , 11 ) X ( 6 , 14 , 7 , 13 ) X ( 9 , 3 , 10 , 2 ) X ( 12 , 17 , 13 , 18 ) X ( 14 , 8 , 15 , 7 ) X ( 16 , 11 , 17 , 12 ) X ( 18 , 15 , 1 , 16 ) {\displaystyle X(1,4,2,5)X(3,9,4,8)X(5,10,6,11)X(6,14,7,13)X(9,3,10,2)X(12,17,13,18)X(14,8,15,7)X(16,11,17,12)X(18,15,1,16)}
