The calculated distance (air line) between Seongnam-si and Hwawŏn is approximately 136 miles respectively 219 kilometers.
By car or train, the actual journey to Hwawŏn is certainly longer, as only the direct route (as the crow flies) between Seongnam-si and Hwawŏn has been calculated here.
Air line (approximately)
219 kilometers
118 nautical miles