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