(2006-1/2-1/3-……-1/2005)(1/2+1/3+……+1/2006)=(2006-1/2-1/3-……-1/2005)(1/2+1/3+……+1/2005)+(2006-1/2-1/3-……-1/2005)*1/2006
(2006-1/2-1/3-……-1/2006)(1/2+1/3……+1/2005)=(2006-1/2-1/3-……-1/2005)(1/2+1/3……+1/2005)-(1/2+1/3……+1/2005)*1/2006
(2006-1/2-1/3-……-1/2005)(1/2+1/3+……+1/2006)-(2006-1/2-1/3-……-1/2006)(1/2+1/3……+1/2005)=(2006-1/2-1/3-……-1/2005)*1/2006+(1/2+1/3……+1/2005)*1/2006
=1