How to evaluate "1"+2+3+4+5=? in JavaScript?

<script language="javascript" type="text/javascript">

        function Evaluate() 

        {

            var i = "1";

            var j = 2;

            var k = 3;

            var l = 4;

            var m = 5;

            alert(i + j + k + l + m);

        }

    </script>

<input type="button" id="calc" value="Click" onclick="Javascript:Evaluate();" />