how to get NaN to number in jQurey?

how to get NaN to number in jQurey?

I am trying this code, but getting the result as NaN. Please give solutions for this.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <script src="Scripts/jquery-1.11.0.min.js " type="text/javascript"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            var v1, v2, res;
            $("#btnAdd").click(function () {
                v1 = $("#txtval1").val();
                v2 = $("#txtval2").val();
                res = parseFloat(v1) + parseFloat(v2);
                $("#result").val(res);

            });
          
        });    
    
    
    </script>


</head>
<body>
    <form id="form1" runat="server">
    <div>
    Enter value 1: <asp:TextBox ID="txtval1" runat="server" ></asp:TextBox><br />

    Enter value 2: <asp:TextBox ID="TextBox2" runat="server" ></asp:TextBox><br />
    <asp:Button ID="btnAdd" runat="server" Text="ADDITION" OnClientClick="return false; "/><br />
   Result: <asp:TextBox ID="result" runat="server" ReadOnly="true"></asp:TextBox><br />
 </div>
    </form>
</body>
</html>