removed hello_world.txt
removed hello_world.txt

yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow