In 2010, how many 1st venue cities were there? 
CREATE TABLE "list_of_fina_diving_world_series" (
  "year" real,
  "1st_venue" text,
  "2nd_venue" text,
  "3rd_venue" text,
  "4th_venue" text,
  "5th_venue" text
);
SELECT COUNT("1st_venue") FROM "list_of_fina_diving_world_series" WHERE "year"=2010;