Name the total number of runner up a for  perambalur
CREATE TABLE "list_of_elected_m_ps" (
  "constituency" text,
  "winner" text,
  "party" text,
  "margin" real,
  "runner_up_a" text,
  "party_a" text
);
SELECT COUNT("runner_up_a") FROM "list_of_elected_m_ps" WHERE "constituency"='Perambalur';