function change(button)
{
       document.getElementById("st"+button).style.backgroundImage="url(images/o1.jpg)";
	   document.getElementById("c"+button).style.backgroundImage="url(images/o2.jpg)";
	   document.getElementById("dr"+button).style.backgroundImage="url(images/o3.jpg)";
}
function retablir(button)
{
       document.getElementById("st"+button).style.backgroundImage="url(images/n1.jpg)";
	   document.getElementById("c"+button).style.backgroundImage="url(images/n2.jpg)";
	   document.getElementById("dr"+button).style.backgroundImage="url(images/n3.jpg)";
}
function retablir_home(button)
{
       document.getElementById("st"+button).style.backgroundImage="url(images/h1.jpg)";
	   document.getElementById("c"+button).style.backgroundImage="url(images/h2.jpg)";
	   document.getElementById("dr"+button).style.backgroundImage="url(images/h3.jpg)";
}