I have accidentally deleted X11

Ihave the OS X LION and I accidentally deleted X11 allowed me to openGIMP. I tried to download it from Apple, but when I go to install itI get the message "I can not install it because there is alreadya newer version."

Probablythe system sees it, but I deleted from recycle bin. How do I restoreit? Thanks for those who want to help me. I have too many jobs storedin the GIMP.