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