What is the lowest capacity with an opening larger than 2015 in Trabzon?
CREATE TABLE "under_construction_stadium_s" (
  "stadium" text,
  "capacity" real,
  "city" text,
  "club" text,
  "opening" real
);
SELECT MIN("capacity") FROM "under_construction_stadium_s" WHERE "opening">2015 AND "city"='trabzon';