The number 2013 is expressed in the form

2013=\dfrac{a_{1} ! a_{2} ! \cdots a_{m} !}{b_{1} ! b_{2} ! \cdots b_{n} !}

where a_{1} \geq a_{2} \geq \cdots \geq a_{m} and b_{1} \geq b_{2} \geq \cdots \geq b_{n} are positive integers and a_{1}+b_{1} is as small as possible. What is \left|a_{1}-b_{1}\right| ?

**Answer Choices**

A. 1

B. 2

C. 3

D. 4

E. 5