When Denizli was the province, what was the total number of valid votes?
CREATE TABLE "results_by_province" (
  "province" text,
  "registered_voters" real,
  "people_voted" real,
  "valid_votes" real,
  "invalid_votes" real,
  "yes" real,
  "yes_pct" text,
  "no" real,
  "no_pct" text,
  "turnout_pct" text
);
SELECT COUNT("valid_votes") FROM "results_by_province" WHERE "province"='Denizli';