How to increase the font size of first two letters of any word/sentence?

How to increase the font size of first two letters of any word/sentence?

I am trying to make the font size bigger for first two letters of nav
links. I know for first letter it can be achieved using :first-letter.
However I have tried it using span like below and it's increasing the font
size but not getting aligned horizontally. About and Contact links are
moving to top, both should be aligned with rest of the links(from bottom).
I don't want to set line-height to the main container because the sub
links are supposed to display below the main links. Any idea about this?
<li><a href="#"><span>01</span> Architectural Design</a></li>
CSS
ul li a span{
font-size:25px;
}
JSFiddle