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_72 (bronze INTEGER, nation VARCHAR, silver VARCHAR)
### Question:
What is the number of bronze for Canada and silver is less than 0?
### Answer:
SELECT SUM(bronze) FROM table_name_72 WHERE nation = "canada" AND silver < 0