a := (  1, 20,  2)(  3, 21, 38)(  4, 22, 39)(  5, 23, 40)(  6, 24, 41)
(  7, 25, 42)(  8, 26, 43)(  9, 27, 44)( 10, 28, 45)( 11, 29, 46)( 12, 30, 47)
( 13, 31, 48)( 14, 32, 49)( 15, 33, 50)( 16, 34, 51)( 17, 35, 52)( 18, 36, 53)
( 19, 37, 54);