When you come to SNU first, you can receive your Alien registration number like yymmdd-1000000(woman is 2000000).
But you have to change your Alien registration number when you receive new number from Korea Immigration office for issuing S-card.

At that time,

1. Please bring your Alien registration card,
2. Visit the EE office (Building 301, Room 319, Ms. Jiyoun Lee)
3.  Write the application form.
4. You can find your new Alien registration number on mysnu website for 3~4 days.