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