What is the highest number of gold medals when the silver is less than 0?
CREATE TABLE table_47309 (
    "Rank" text,
    "Nation" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real,
    "Total" real
)
SELECT MAX("Gold") FROM table_47309 WHERE "Silver" < '0'
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 is the highest number of gold medals when the silver is less than 0? ### Input: CREATE TABLE table_47309 (
    "Rank" text,
    "Nation" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real,
    "Total" real
) ### Response: SELECT MAX("Gold") FROM table_47309 WHERE "Silver" < '0'