WASHINGTON (AP) — President Barack Obama said Friday that suggestions from people like Donald Trump that nuclear weapons would help South Korea and Japan show a lack of understanding of the world.The Republican presidential front-runner told The New York Times last week he would be open to Japan and South Korea having their own atomic arsenals as a deterrent to North Korea.When asked about the issue Friday night, Obama said, "The person who made the statements doesn't know much about foreign policy or nuclear policy or the Korean Peninsula or the world generally."He described the U.S.