2002@2004@2006@2008@2010
=(2002+2004)/2@2006@2008@2010
=2003@2006@2008@2010
=(2003+2006+1)/2@2008@2010
=2005@2008@2010
=(2005+2008+1)/2@2010
=2007@2010
=(2007+2010+1)/2
=2009
结果为2009
(2002+2004)÷2=2003
(2003+2006+1)÷2=2005
(2005+2008+1)÷2=2007
(2007+2010+1)÷2=2009
2009