what is the number of relapsing fever when malaria is 3000
CREATE TABLE "incidence_of_disease_in_russian_empire_a" (
  "year" text,
  "typhus" real,
  "typhoid_fever" real,
  "relapsing_fever" real,
  "smallpox" real,
  "malaria" text
);
SELECT MIN("relapsing_fever") FROM "incidence_of_disease_in_russian_empire_a" WHERE "malaria"='3000';