function calcola() {
	//var main_div = document.getElementById('main_div');
	var cen_div = document.getElementById('cen');
	var dx_div = document.getElementById('dx');
	var sx = document.getElementById('sx').offsetHeight;
	var cen = document.getElementById('cen').offsetHeight;
	var cen = cen_div.offsetHeight;
	var dx = document.getElementById('dx').offsetHeight;
	var last_div_height = document.getElementById('last_div').offsetHeight;	
	var last_div_top = document.getElementById('last_div').offsetTop;
	var yy = document.getElementById('last_div').style.offsetY;
	//var credits = document.getElementById('credits').style.top;	
	//last_div_top = last_div_top.substring(0,last_div_top.length-2);
	cen_ori = cen;
	//alert(last_div_top + " - " + last_div_height + " -  " + cen);
	cen = parseInt(last_div_top) + parseInt(last_div_height);	
	//alert(cen);
	if (sx>cen) {
		if(sx>dx) {
			altezza = sx;
		}
		else {
			altezza = dx;
		}
	}
	else {
		if(cen>dx) {
			altezza = cen;
		}
		else {
			altezza = dx;
		}
	}

	postop = sx + cen_ori - 12;
	//alert(altezza);
	document.getElementById('main_div').style.height = altezza + "px"; //altezza
	document.getElementById('cen').style.top = -sx + "px"; //altezza	
	dx_div.style.top = -postop + "px";
}