Given a document, generate a short title of the document. The title should convey the main idea/event/topic about which the document is being written. Note that URLs in the text have been replaced with [Link].
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Question: MOSCOW (Reuters) - Russia will supply Turkey with four batteries of S-400 surface-to-air missiles for $2.5 billion under a deal that is almost complete  Sergei Chemezov  head of Russian state conglomerate Rostec  told the Kommersant daily on Wednesday.
Turkey will pay 45 percent of the cost up front with Russia providing loans to cover the remaining 55 percent   Chemezov  said. Moscow expected to begin the first deliveries in March 2020   he  said.
 Chemezov  told Kommersant that Turkey was the first NATO member state to acquire the advanced S-400 missile system.
 He  said the Russian and Turkish finance ministries had already completed talks on financing the deal and that the final documents just needed to be approved.

Answer: Russia to supply Turkey with four S


Question: The flying taxi developed by German drone firm Volocopter  resembles a small  two-seater helicopter cabin topped by a wide hoop studded with 18 propellers.
 It  was unmanned for  its  maiden test run in a ceremony arranged for Dubai Crown Prince Sheikh Hamdan bin Mohammed.
 Volocopter  is in a race with more than a dozen well-funded European and U.S. firms  each with  its  own science fiction-inspired vision for creating a new form of urban transport that is a cross between a driverless electric car and a short-haul  vertical takeoff-and-landing aircraft.
“Implementation would see you using your smartphone  having an app  and ordering  a Volocopter  to the next voloport near you.  The volocopter  would come and autonomously pick you up and take you to your destination ” CEO Florian Reuter said.

Answer: Dubai starts tests in bid to become first city with flying taxis


Question: The armed forces officially took over Rio's police on Friday under a decree signed by President Michel Temer.
 Temer 's extraordinary decree came after Rio's governor asked for federal help following an exceptionally violent Carnival. During the holiday  there were several muggings  armed robberies and violent confrontations.
 Temer  met Monday with ministers and lawmakers to discuss the intervention.
Hours before Congress was to take up the measure  an opposition party asked the Supreme Court to suspend the vote  saying  Temer  had not followed the rules for issuing such a decree and saying the move had "political and electoral motivations." No ruling had come from the top court by the time the session began.
 Temer  and  his  ministers have gone to great lengths to emphasize that the president is ultimately in charge of the operation  providing civilian oversight of the military. That reflects deep unease in a society where many still remember the 1964-1985 military regime.

Answer:
Rio could be 'laboratory' for solving Brazil's crime crisis