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