var bg = new Array(12);
bg[0] = "img/headerbg_wi.jpg";
bg[1] = "img/headerbg_wi.jpg";
bg[2] = "img/headerbg_sp.jpg";
bg[3] = "img/headerbg_sp.jpg";
bg[4] = "img/headerbg_sp.jpg";
bg[5] = "img/headerbg_su.jpg";
bg[6] = "img/headerbg_su.jpg";
bg[7] = "img/headerbg_su.jpg";
bg[8] = "img/headerbg_fa.jpg";
bg[9] = "img/headerbg_fa.jpg";
bg[10] = "img/headerbg_fa.jpg";
bg[11] = "img/headerbg_wi.jpg";
function bg_auto()
	{
	var month = new Date().getMonth();
	document.body.background = bg[month];
	}