The calculated distance (air line) between Yuzhnoukrayinsk and Pervomaysk is approximately 21 miles respectively 34 kilometers.
By car or train, the actual journey to Pervomaysk is certainly longer, as only the direct route (as the crow flies) between Yuzhnoukrayinsk and Pervomaysk has been calculated here.
Air line (approximately)
34 kilometers
18 nautical miles