Alternative solution:
Pair the numbers up as follows
1 | 2010 |
2 | 2009 |
3 | 2008 |
4 | 2007 |
5 | 2006 |
... | |
1004 | 1007 |
1005 | 1006 |
We can see that there are 2010/2=1005 rows, and the sum of each row is 2011, which is equal to 1 modulo 2010, thus the answer is
1005*1 = 1005
Hope this helped :)