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