Who was the leader at the summit earlier than 1956, when Carcassonne shows for finish?
CREATE TABLE "appearances_in_tour_de_france_since_1947" (
  "year" real,
  "stage" real,
  "start" text,
  "finish" text,
  "leader_at_the_summit" text
);
SELECT "leader_at_the_summit" FROM "appearances_in_tour_de_france_since_1947" WHERE "year"<1956 AND "finish"='carcassonne';