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