A circle has center $G$, and points $M$ and $N$ lie on the circle. Line segments $MH$ and $NH$ are tangent to the circle at points $M$ and $N$, respectively. If the radius of the circle is 15 centimeters and the distance between points $G$ and $H$ is 17 centimeters, what is the perimeter, in centimeters, of quadrilateral $GMHN$?