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_52 (year_opened INTEGER, main_span_feet VARCHAR, country VARCHAR)
### Question:
What is the oldest year with a main span feet of 1,640 in South Korea?
### Answer:
SELECT MIN(year_opened) FROM table_name_52 WHERE main_span_feet = "1,640" AND country = "south korea"