var show = 2;

function swap()
{
	switch(show)
	{
		case 1:
			document.getElementById("left2").style.visibility = "hidden";
			document.getElementById("left3").style.visibility = "hidden";
			show = 2;
			break;
		case 2:
			document.getElementById("left2").style.visibility = "visible";
			document.getElementById("left3").style.visibility = "hidden";
			show = 3;
			break;
 		case 3:		
			document.getElementById("left2").style.visibility = "hidden";
			document.getElementById("left3").style.visibility = "visible";
			show = 1;
			break;
	}
}