It is not a very good idea to call someone who you don't know 아줌마, 아저씨, or 아가씨. 청년 or 학생 can be OK but sometimes not especially when you are younger than them. Just say '저기요' or '실례합니다'. It will help you avoid mistakes or rudeness. (This is for a real conversation, not for written Korean.)

к молодой девушке обратиться "аджума" ))), я под столом ахахаха...