SCHEMA:
CREATE TABLE table_name_31 (year_of_disaffiliation INTEGER, station VARCHAR, year_of_affiliation VARCHAR)
USER:
What is the most recent year of disaffiliation of a CHCH-TV station that affiliated after 2001?

QUERY:
SELECT MAX(year_of_disaffiliation) FROM table_name_31 WHERE station = "chch-tv" AND year_of_affiliation > 2001