unable to connect with SharePoint site using CSOM

Question

I am trying to connect to SharePoint 2013 site with CSOM using a function with 2 arguments. When i am giving only $x that is site URL as argument then code is working fine but when i am giving two arguments to function then it is not working.

Error is

New-Object : Cannot find an overload for "ClientContext" and the argument count: "2". At line:3 char:9 + $ctx = New-Object Microsoft.SharePoint.Client.ClientContext($z) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (:) [New-Object], MethodException + FullyQualifiedErrorId : ConstructorInvokedThrowException,Microsoft.PowerShell.Commands.NewObjectCommand .

Please help as i am new to SharePoint Powershell.

[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint.Client")
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint.Client.Runtime")

    function a($x,$y){
     $ctx = New-Object Microsoft.SharePoint.Client.ClientContext($x)
        $ctx.Credentials = New-Object System.Net.NetworkCredential($loginname,$pwd) 
        $web=$ctx.web 
        $ctx.load($web)
        $ctx.ExecuteQuery()
        $web.Url
    }
    $pwd = Read-Host "Enter Password of SharePoint 2013 site owner "-AsSecureString
    $loginname = "username"
    $x = "https://cortona.sharepoint2013.com/sites/abc"
    $y = 2
    a($x,$y)