user: Question: Which country's material was concrete when the span metres were less than 270, span feet is more than 837, and the year opened was 1943?
Columns: ['Rank', 'Name', 'Span metres', 'Span feet', 'Material', 'Year opened', 'Country']
Types: ['real', 'text', 'real', 'real', 'text', 'text', 'text']
Sample row: [1.0, 'Chaotianmen Bridge', 552.0, 1811.0, 'steel', '2009', 'China']
SQL:

assistant: SELECT "Country" FROM "Table" WHERE "Material" = 'concrete' AND "Span metres" < 270.0 AND "Span feet" > 837.0 AND "Year opened" = '1943';