What series number had an original airdate of March 1, 1991?
CREATE TABLE table_26540 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real
)
SELECT MIN("No. in series") FROM table_26540 WHERE "Original air date" = 'March 1, 1991'
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 series number had an original airdate of March 1, 1991? ### Input: CREATE TABLE table_26540 (
    "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 MIN("No. in series") FROM table_26540 WHERE "Original air date" = 'March 1, 1991'