Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_43 (week INTEGER, opponent VARCHAR)
### Question:
Opponent of at san francisco 49ers had what lowest week?
### Answer:
SELECT MIN(week) FROM table_name_43 WHERE opponent = "at san francisco 49ers"