PRESIDENT OBAMA:  Xin chào!  (Applause.)  Xin chào Vietnam!  (Applause.)  Thank you.  Thank you so much.  To the government and the people of Vietnam, thank you for this very warm welcome and the hospitality that you have shown to me on this visit.  And thank all of you for being here today.  (Applause.)   We have Vietnamese from across this great country, including so many young people who represent the dynamism, and the talent and the hope of Vietnam