What should travelers know about choosing travel insurance for a visit to Ukraine, especially if they are entering the country by different types of border crossings, and are there any specific insurance requirements or coverage details they should check in advance to make sure their policy is accepted when crossing the Ukrainian border? I’m also curious whether the same requirements apply to travelers arriving by air, train, car, or bus, and what documents they may need to have available during border control if an officer asks for proof of valid medical or travel insurance.