function Cena() {
	var plus = 0; var m = 0; var n = 0;
	var datum = new Date();
	with (datum) m = getMonth();
	if (m > 3) n = 100;
	else n = 0;
		if (document.getElementById('pulmarat').checked) plus += 500 + n;
		if (document.getElementById('marathon').checked) plus += 600 + n;
		if (document.getElementById('ultra90').checked)  plus += 700 + n;
		if (document.getElementById('ultra103').checked) plus += 700 + n;
		if (document.getElementById('dvojice').checked)  plus +=1200 + n + n;
	var a = document.getElementById('seminar').value * 100;
	var b = document.getElementById('vecirek').value * 120;
	plus = plus + a + b;
	document.ff.celkem.value = plus;
}