a := (  1, 19,  2)(  3, 20, 36)(  4, 21, 37)(  5, 22, 38)(  6, 23, 39)
(  7, 24, 40)(  8, 25, 41)(  9, 26, 42)( 10, 27, 43)( 11, 28, 44)( 12, 29, 45)
( 13, 30, 46)( 14, 31, 47)( 15, 32, 48)( 16, 33, 49)( 17, 34, 50)
( 18, 35, 51);