<body>
<section>
<h1>Calculator</h1>
<label class="sum">Sum:</label>
<input type="text" id="sum" disabled="disabled">
<br>
<label>First Number:</label>
<input type="text" id="firstNumber">
<br>
<label>Second Number:</label>
<input type="text" id="secondNumber">
<br>
<div>
<input type="button" id="calc" value="Calculate">
<input type="button" id="clear" value="Clear">
</div>
</section>
</body>