a := (  1, 15,  2)(  3, 16, 28)(  4, 17, 29)(  5, 18, 30)(  6, 19, 31)
(  7, 20, 32)(  8, 21, 33)(  9, 22, 34)( 10, 23, 35)( 11, 24, 36)( 12, 25, 37)
( 13, 26, 38)( 14, 27, 39);