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