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