Ban Ki-moon (L), former Secretary-General of the United Nations, smiles on the train of the Airport Express from Incheon to the railway station in Seoul, South Korea, Jan. 12, 2017. Former UN Secretary-General Ban Ki-moon on Thursday tried hard to show his people-friendly identity as he returned to his home country, South Korea, following the end of his 10-year tenure in the top UN post. (Xinhua/Lee Sang-ho)