In which series was season 18?
CREATE TABLE table_26568 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real
)
SELECT COUNT("No. in series") FROM table_26568 WHERE "No. in season" = '18'
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: In which series was season 18? ### Input: CREATE TABLE table_26568 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real
) ### Response: SELECT COUNT("No. in series") FROM table_26568 WHERE "No. in season" = '18'