Trisect a Median

Geometry Level 3

In the diagram above, suppose that $BA_{1} = A_1A_2 = A_2C$ and $AC_1 = C_1B$ . If $C_1Y = 2017$ , then $XY = \frac{p}{q}$ , where $p$ and $q$ are coprime positive integers. Find $p + q$ .