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