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