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