What's the smallest pick number of a player playing in Minnesota North Stars?
CREATE TABLE "round_four" (
  "pick_num" real,
  "player" text,
  "position" text,
  "nationality" text,
  "nhl_team" text,
  "college_junior_club_team" text
);
SELECT MIN("pick_num") FROM "round_four" WHERE "nhl_team"='Minnesota North Stars';