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