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