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