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