BAMO 2012 Problem 3

Two infinite rows of evenly-spaced dots are aligned as in the figure below. Arrows point from every dot in the top row to some dot in the lower row in such a way that:

1- No two arrows point at the same dot.
2- No arrow can extend right or left by more than 1006 positions.

Show that at most 2012 dots in the lower row could have no arrow pointing to them.