The calculated distance (air line) between Hwangju-ŭp and Hŭngnam is approximately 128 miles respectively 206 kilometers.
By car or train, the actual journey to Hŭngnam is certainly longer, as only the direct route (as the crow flies) between Hwangju-ŭp and Hŭngnam has been calculated here.
Air line (approximately)
206 kilometers
111 nautical miles