AMC 12 2003a Problem 1

What is the difference between the sum of the first $2003$ even counting numbers and the sum of the first $2003$ odd counting numbers?

$\mathrm{(A) \ } 0 \mathrm{(B) \ } 1 \mathrm{(C) \ } 2 \mathrm{(D) \ } 2003 \mathrm{(E) \ } 4006$