I need to copy content from one div to another one with changing button's id (increment them)

Sample:

```
<script type="text/javascript">
  function add(){
    document.getElementById('two').innerHTML = document.getElementById('one').innerHTML;
  }
</script>

<div id="one">
  <button id="button_1" >Button_1</button>
</div>

<div id="two"></div>

<button onclick="add();">Add</button>

```

This of course can't work properly.

Result should be following:

```
<div id="two">
  <button id="button_2" >Button_2</button>
</div>

```

Any simple way how to do this ?