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