function getSum() {
	r1 = document.getElementById('r1').value;
	r2 = document.getElementById('r2').value;
	r3 = document.getElementById('r3').value;
	w1 = document.getElementById('w1').value;
	w2 = document.getElementById('w2').value;
	d1 = document.getElementById('d1').value;
	d2 = document.getElementById('d2').value;

	s = (r1*2 + r2*2)*r3;
	real = s - (w1*w2 + d1*d2);
	document.getElementById('calc_val').style.display = 'block';
	document.getElementById('calc_val').value = 'Необходимо '+real+' кв.м. обоев';
}