Write SQL query to solve given problem: How many days was the fastest shipping of Berglunds snabbkp's order?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT datediff(T2.ShippedDate, T2.OrderDate) FROM Customers AS T1 INNER JOIN Orders AS T2 ON T1.CustomerID = T2.CustomerID WHERE T1.CompanyName = 'Berglunds snabbkp' ORDER BY datediff(T2.ShippedDate, T2.OrderDate) LIMIT 1