x=0;
function autoImgFlip() {
	setTimeout("autoImgFlip()", 3000);

	switch (x){
		case 0:
			document.getElementById('cambia').style.backgroundImage="url(img/0.jpg)";
			x++;
		break;
		case 1:
			document.getElementById('cambia').style.backgroundImage="url(img/1.jpg)";
			x++;
		break;
		case 2:
			document.getElementById('cambia').style.backgroundImage="url(img/2.jpg)";
			x++;
		break;
		case 3:
			document.getElementById('cambia').style.backgroundImage="url(img/3.jpg)";
			x++;
		break;
	}
}