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