Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the average silver that has a gold greater than 3, with soviet union (urs) as the nation, and a bronze greater than 26?

### Inputs:
table_name: table, columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']

### Response:
SELECT AVG Silver FROM table WHERE Gold > 3 AND Nation = soviet union (urs) AND Bronze > 26