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US President Barack Obama leaves in Air Force One from the airport Langenhagen near Hanover, central Germany, on April 25, 2016. Obama is in Germany on the last leg of his tour of Europe and the Gulf, planning to underscore close ties with Chancellor Angela Merkel and make the case for a controversial transatlantic free trade agreement (TTIP). / AFP / Ronny HARTMANN / ALTERNATIVE CROP (Photo credit should read RONNY HARTMANN/AFP/Getty Images)

US President Barack Obama leaves in Air Force One from the airport Langenhagen near Hanover, central Germany, on April 25, 2016.
Obama is in Germany on the last leg of his tour of Europe and the Gulf, planning to underscore close ties with Chancellor Angela Merkel and make the case for a controversial transatlantic free trade agreement (TTIP). / AFP / Ronny HARTMANN / ALTERNATIVE CROP         (Photo credit should read RONNY HARTMANN/AFP/Getty Images)