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