X ( 2 , 9 , 3 , 10 ) X ( 4 , 13 , 5 , 14 ) X ( 6 , 7 , 1 , 8 ) X ( 8 , 1 , 9 , 2 ) X ( 10 , 3 , 11 , 4 ) X ( 11 , 18 , 12 , 19 ) X ( 14 , 5 , 15 , 6 ) X ( 15 , 20 , 16 , 21 ) X ( 17 , 22 , 18 , 7 ) X ( 19 , 12 , 20 , 13 ) X ( 21 , 16 , 22 , 17 ) {\displaystyle X(2,9,3,10)X(4,13,5,14)X(6,7,1,8)X(8,1,9,2)X(10,3,11,4)X(11,18,12,19)X(14,5,15,6)X(15,20,16,21)X(17,22,18,7)X(19,12,20,13)X(21,16,22,17)}