Search Query Parameter changing from /?s=Keyword to /?q=KEYWORD

Hello,

My wordpress blog is http://www.education.gainsearch.com if i search anything it is showing url like http://www.education.gainsearch.com/?s=KEYWORD

But i want “q” insted of “s” like the following

http://www.education.gainsearch.com/?q=KEYWORD

Can any one help me where to change or how to do that

Because i want to integrate this with adsense Search, in that adsense search they are passing KEYWORD in “q”

If the above is possible simply i can display Adsense search results and WordPress search results both in same page