function zmen(){
var cena;
var cenaCelkem = 0;
var snidane;
var post = "";
var cena1 = 0;
var cena2 = 0;
var cena3 = 0;
var pokoj1 = document.getElementById("a");
var pokoj2 = document.getElementById("b");
var pokoj3 = document.getElementById("c");
var kolik1 = document.getElementById("kolik1").value;
var kolik2 = document.getElementById("kolik2").value;
var kolik3 = document.getElementById("kolik3").value;
var pocetMist = 0;
snidanee = document.getElementById("snidane");

jazyk = document.getElementById("jazyk").value;

if(snidanee.checked){
snidane = 120;
}else{
snidane = 0;
}

if(pokoj1.checked){
cena1 = 990*kolik1;
pocetMist = pocetMist + 1*kolik1;
}else{
cena1 = 0;
}

if(pokoj2.checked){
cena2 = 1450*kolik2;
pocetMist = pocetMist + 2*kolik2;
}else{
cena2 = 0;
}

if(pokoj3.checked){
cena3 = 1800*kolik3;
pocetMist = pocetMist + 4*kolik3;
}else{
cena3 = 0;
}

denOd = document.getElementById("denOd").value;
mesicOd = document.getElementById("mesicOd").value;
rokOd = document.getElementById("rokOd").value;

denDo = document.getElementById("denDo").value;
mesicDo = document.getElementById("mesicDo").value;
rokDo = document.getElementById("rokDo").value;

var ted = new Date();
var dni = new Date(new Date(rokDo, mesicDo-1, denDo, 0, 0, 0) - new Date(rokOd, mesicOd-1, denOd, 0, 0, 0));
dni = Math.round(dni.getTime()/86400000);

cenaCelkem = dni*cena1*0.9 + dni*cena2*0.9 + dni*cena3*0.9 + dni*snidane*pocetMist;

celkem = document.getElementById("celkem");

if(cenaCelkem<0){
cenaCelkem = 0;
}

if(jazyk=="cs"){
post = ",-- Kč";
}else if(jazyk=="en"){
post = " CZK";
}else{
post = " CZK";
}
cena = Math.round(cenaCelkem);
celkem.value = cena + post;
}