document.onkeyup = KeyCheck;
 
	function KeyCheck(e)
		{
		   var KeyID = (window.event) ? event.keyCode : e.keyCode;
 
		   switch(KeyID)
		   {
 
		      case 37:
		      	show_image(currentImage - 1);
		      break;
 
 
		      case 39:
		      show_image(currentImage + 1);
		      break;

		   }
		}