2003 AMC 12A 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\qquad \mathrm{(B) \ } 1\qquad \mathrm{(C) \ } 2\qquad \mathrm{(D) \ } 2003\qquad \mathrm{(E) \ } 4006

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.