Question: Which Russian mathmatician contributed to number theory, Grigori Perelman or Ivan Fesenko?
Sentence (from "Grigori Perelman"): Grigori Yakovlevich Perelman (Russian: Григо́рий Я́ковлевич Перельма́н ; ] ; born 13 June 1966) is a Russian mathematician.
Relevant evidence: Yes