Coordinate Geometry: Midpoint of Two Points

The triangle $ABC$ lies on the coordinate plane. The midpoint of $\overline{AB}$ has coordinates $(-16, -63)$, the midpoint of $\overline{AC}$ has coordinates $(13, 50)$, and the midpoint of $\overline{BC}$ has coordinates $(6, -85)$. What is the sum of the coordinates of point $A$?

Source: Math Prize for Girls