What is the highest number of games won where less than 21 games were conceded and less than 18 games were actually played?
CREATE TABLE "clausura_2007_standings" (
  "place_posici_n" real,
  "team_equipo" text,
  "played_pj" real,
  "won_pg" real,
  "draw_pe" real,
  "lost_pp" real,
  "goals_scored_gf" real,
  "goals_conceded_gc" real,
  "dif" real,
  "points_pts" real
);
SELECT MAX("won_pg") FROM "clausura_2007_standings" WHERE "goals_conceded_gc"<21 AND "played_pj"<18;