1 + 2-3-4 + 5 + 6-7-8 + 9 + 10. It is a continuous integer starting from 1. Take two positive and two negative in turn. What is the sum of the first 2006 numbers in this series

1 + 2-3-4 + 5 + 6-7-8 + 9 + 10. It is a continuous integer starting from 1. Take two positive and two negative in turn. What is the sum of the first 2006 numbers in this series

1+2-3-4+5+6-7-8+9+10.+2005+2006
=(1+2-3-4)+(5+6-7-8)+.+(2001+2002-2003-2004)+2005+2006
=(-4)+(-4)+.+(-4)+2005+2006
=(-4)*2004/4 +2005+2006
=2007