[U.N. Secretary General Ban Ki-moon, left, is welcomed by Greek Prime Minister Alexis Tsipras in Athens, on Saturday, June 18, 2016. The United Nations secretary-general is visiting a charity in Athens, ahead of talks with Greek government officials and a trip to the island of Lesbos, which is at the forefront of Greece's immigration crisis. (AP Photo/Yorgos Karahalis)]ATHENS, Greece (AP) — The United Nations secretary-general has congratulated Greece for its assistance to more than a million refugees and other migrants who have flowed through the country toward Europe's prosperous heartland.