Table schema:
CREATE TABLE table_name_78 (silver INTEGER, bronze VARCHAR, total VARCHAR, gold VARCHAR)

Question: What is the most silver medals won among nations that won more than 40 medals total, less than 25 of them being gold, and more than 15 of them being bronze?
SQL: SELECT MAX(silver) FROM table_name_78 WHERE total > 40 AND gold < 25 AND bronze > 15