The Main CEU Entrance is in Budapest, District 5, at Nador u. 9 (u. is an abbreviation for utca = street). This is on the corner of Nador u. and Zrinyi u. All Mathematics Dept offices/classroom are located at Zriunyi u. 14, very close to the corner of Zrinyi u. and Oktober 6 u. (The second building after the bronze policeman statue.) We are on the third floor.
Further information on the CEU campus and access is available here: http://www.ceu.hu/campus