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_7 (silver INTEGER, nation VARCHAR, gold VARCHAR)
### Question:
What is the sum of silver medals of the nation Cuba, which has less than 0 gold?
### Answer:
SELECT SUM(silver) FROM table_name_7 WHERE nation = "cuba" AND gold < 0