user: Question: What was the total number of weeks with a result of l 31-21?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 26, 1949', 'at Chicago Cardinals', 'L 38-7', 24136.0]
SQL:

assistant: SELECT COUNT("Week") FROM "Table" WHERE "Result" = 'l 31-21';