1+2+3-4-5-6+7+8+9- ...-2002-2003-2004
=(1+2+3-4-5-6)+(7+8+9-10-11-12)+ ...+(1999+2000+2001-2002-2003-2004)
=-9-9-9-...-9
=-9*334
=-3006
1+2+3-4-5-6+7+8+9- ...-2002-2003-2004
=(1+2+3-4-5-6)+(7+8+9-10-11-12)+ ...+(1999+2000+2001-2002-2003-2004)
=-9-9-9-...-9
=-9*334
=-3006