function getkey(e){if(window.event)return window.event.keyCode;else if(e)return e.which;else return null;}
		
function goodchars(e, goods){
	var key, keychar;
	key = getkey(e);
	if (key == null) return true;
	keychar = String.fromCharCode(key);
	keychar = keychar.toLowerCase();
	goods = goods.toLowerCase();
	if (goods.indexOf(keychar) != -1) return true;
	if ( key==null || key==0 || key==8 || key==9 || key==13 || key==27 ) return true;
	return false;
}
			
function calc(){
	if  (document.getElementById("x1").value != "" ){
		rez_exact = parseFloat(document.getElementById("x1").value) * parseFloat(document.getElementById("c1").value)/	parseFloat(document.getElementById("c2").value);
		document.getElementById("rez").value = Math.round(rez_exact*100)/100;
		document.getElementById("tva").value = Math.round(rez_exact*100*0.19)/100;
		document.getElementById("rez_final").value = Math.round(rez_exact*100*1.19)/100;
	}
	else{
		document.getElementById("rez").value = "";
		document.getElementById("tva").value = "";
		document.getElementById("rez_final").value = "";
	}
}