var totalImgs = 4; // Total number of images to loop
var i = 1;
function nextImg()
{
	if (i <= totalImgs)	{
		document.getElementById('mastImg').src = 'images/mast_photos/' + i + '.jpg';
		i++;
	}
	else {
		i = 1;
		document.getElementById('mastImg').src = 'images/mast_photos/' + i + '.jpg';
	}
	setTimeout('nextImg()', 5000);
}