What's the series number of the episode seen by 2.43 million viewers in the UK?
CREATE TABLE table_19236587_4 (
    series_no VARCHAR,
    uk_viewers__million_ VARCHAR
)
SELECT series_no FROM table_19236587_4 WHERE uk_viewers__million_ = "2.43"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What's the series number of the episode seen by 2.43 million viewers in the UK? ### Input: CREATE TABLE table_19236587_4 (
    series_no VARCHAR,
    uk_viewers__million_ VARCHAR
) ### Response: SELECT series_no FROM table_19236587_4 WHERE uk_viewers__million_ = "2.43"