|2009/1-2008/1|+|2008/1-2007/1|+|2007/1-2006/1|+.+|3/1-2/1|+|2/1-1|
=1/2008-1/2009+1/2007-1/2008+1/2006-1/2007+.+1/2-1/3+1-1/2
=1-1/2009
=2008/2009