What is the latest year that chou tien-chen played men's singles?
CREATE TABLE "21st_century" (
  "year" real,
  "men_s_singles" text,
  "women_s_singles" text,
  "men_s_doubles" text,
  "women_s_doubles" text,
  "mixed_doubles" text
);
SELECT MAX("year") FROM "21st_century" WHERE "men_s_singles"='chou tien-chen';