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