var backgroundNumber = 1;
var bgTimer = null;
var clockTimer = null;
function flipImage(number) {
	if(number<=4) {
		backgroundNumber = number;
		document.getElementById('main-image').src = 'images/main_'+backgroundNumber+'.png';
		// cache next image
		var nextImage = (backgroundNumber+1);
		//alert(nextImage);
		objImage = new Image();
		objImage.src='images/main_'+nextImage+'.jpg';
		//
		setTimeout("flipImage("+nextImage+");", 6000);
	}
	else {
		number = Math.floor(Math.random()*1)+1;
		if(number>1) {
			number = Math.floor(Math.random()*3)+2;
		}
		setTimeout("flipImage("+number+");", 1000);
	}
}
number = Math.floor(Math.random()*4)+1;



function isNumberKey(evt) {
	var charCode = (evt.which) ? evt.which : event.keyCode
	if (charCode > 31 && (charCode < 48 || charCode > 57))
	return false;
	
	return true;
}