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