var sichtbar = 0;

function naviclose(x1) {
  sichtbar = x1;
  document.getElementById("navi" + x1).style.visibility = "visible";
}	
	
function navian(x2) {
  document.getElementById("navi" + x2).style.visibility = "visible";
}

function naviaus(x3) {
  if (x3 != sichtbar) {
    document.getElementById("navi" + x3).style.visibility = "hidden";
  }
}