X ( 2 , 9 , 3 , 10 ) X ( 4 , 19 , 5 , 20 ) X ( 5 , 14 , 6 , 15 ) X ( 8 , 11 , 1 , 12 ) X ( 10 , 1 , 11 , 2 ) X ( 12 , 3 , 13 , 4 ) X ( 15 , 21 , 16 , 20 ) X ( 16 , 7 , 17 , 8 ) X ( 18 , 14 , 19 , 13 ) X ( 21 , 6 , 22 , 7 ) X ( 22 , 18 , 9 , 17 ) {\displaystyle X(2,9,3,10)X(4,19,5,20)X(5,14,6,15)X(8,11,1,12)X(10,1,11,2)X(12,3,13,4)X(15,21,16,20)X(16,7,17,8)X(18,14,19,13)X(21,6,22,7)X(22,18,9,17)}