What is the maximum pick when WR was the position and Michigan the college, and the overall greater than 255?
CREATE TABLE "washington_redskins_draft_history" (
  "round" real,
  "pick" real,
  "overall" real,
  "name" text,
  "position" text,
  "college" text
);
SELECT MAX("pick") FROM "washington_redskins_draft_history" WHERE "position"='wr' AND "college"='michigan' AND "overall">255;