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