var n = 11;
var f = false;
var b = new Array;

function prel(){
	for(i=1;i<=n;i++){
		str = 'buttons/b' + i + '_o.gif';
		b[i-1] = new Image();
		b[i-1].src = str;
	}
	f = true;
}

function on(im){
	document.images[im].src="buttons/"+im+"_o.gif";
}

function off(im){
	document.images[im].src = "buttons/"+im+".gif";
}