How many years did pia pajunen nina sundberg win women's doubles?
CREATE TABLE "past_winners" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);
SELECT COUNT("year") FROM "past_winners" WHERE "women_s_doubles"='pia pajunen nina sundberg';