Cannot convert classic to claim in sharepoint 2013

Hi ,

I run the cmdlet from msdn

I using the new-spwebapplication to create a classic webapplication in sharepoint 2013, then attach the old database, and then I run the convert,

Convert-SPWebApplication -Identity "http://myspserver" -To Claims –RetainPermissions [-Force]

It does not accept force , how do I write it?

but I get error:

PS C:\Users\Administrator> Convert-SPWebApplication -Identity "http://svrtest01
" -To Claims  -RetainPermissions [-Force]
Convert-SPWebApplication : A positional parameter cannot be found that accepts
argument '[-Force]'.
At line:1 char:1
+ Convert-SPWebApplication -Identity "http://svrtest01" -To Claims
-RetainPermis ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
    + CategoryInfo          : InvalidArgument: (:) [Convert-SPWebApplication],
    ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.SharePoint
   .PowerShell.SpCmdletConvertWebApplication

PS C:\Users\Administrator>