var pre;

function Set(num,img) {
	document.getElementById("l"+num).src=pre+"l"+img;
	document.getElementById("m"+num).style.backgroundImage='url('+pre+'m'+img+')';
	document.getElementById("r"+num).src=pre+"r"+img;
}

function Preload(img) {
  a = new Image(); a.src = pre+"l"+img;
  b = new Image(); b.src = pre+"m"+img;
  c = new Image(); c.src = pre+"r"+img;
}