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