X ( 2 , 5 , 3 , 6 ) X ( 4 , 7 , 1 , 8 ) X ( 6 , 1 , 7 , 2 ) X ( 8 , 3 , 5 , 4 ) {\displaystyle X(2,5,3,6)X(4,7,1,8)X(6,1,7,2)X(8,3,5,4)}