Accepting And Adding Two Numbers in JavaScript

<!DOCTYPE HTML>
    <html>
        <body>
            <input type="text" placeholder="Enter first number" id="fnum"/>
            <br>
            <input type="text" placeholder="Enter second number" id="snum"/>
            <br>
            <button type="button" onclick="addition()">Submit</button>

        <script>
            function addition()
            {
            var a=Number(document.getElementById('fnum').value);
            var b=Number(document.getElementById('snum').value);
            var c=a+b;
            document.write("The sum is "+c);
            }
        </script>

        </body>
    </html>