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 ( 12 , 15 , 13 , 16 ) X ( 14 , 5 , 15 , 6 ) X ( 16 , 11 , 7 , 12 ) {\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(12,15,13,16)X(14,5,15,6)X(16,11,7,12)}