Wirelessly posted (Opera/9.50 (J2ME/MIDP; Opera Mini/4.1.11355/546; U; en))
Technically, this is considered hidden-city ticketing, and the airline could ask you to pay a higher fare.
However, in practice, nothing is likely to happen. When you miss that first flight all the rest of the segments on the itinerary will get cancelled. So make sure you're not trying to fly any other segments. If you make a habit of doing this then you may attract attention...
Good luck
Nick