(1/2008-1)(1/2007-1)(1/2006-1)……(1/1001-1)(1/1000-1)
=(-2007/2008)(-2006/2007)(-2005/2006)...(-1000/1001)(-999/1000)
=-999/2008
(1/2008-1)(1/2007-1)(1/2006-1)……(1/1001-1)(1/1000-1)
=(-2007/2008)(-2006/2007)(-2005/2006)...(-1000/1001)(-999/1000)
=-999/2008