+399 We can see that \(1-2 = -1\), \(3 - 4 = -1\), ... all the way to \(2005-2006 = -1\). \(2007\) has no pair, so we will save that number for later. There are \(1003\) pairs of numbers, which means there are one thousand and three \(-1\)'s. So we have \(-1003 + 2007 = 1004\).
- Daisy
