function show_technicke(num){
  o= this.document.getElementById('imgtex');
  o.src= 'poptavka/img/okna-technicke'+num+'.jpg';
  jeb2= document.getElementById('i2').style;
  jeb3= document.getElementById('i3').style;
  if (show[num] >= 2) jeb2.display= 'block';
  else jeb2.display= 'none';

  if (show[num] >= 3) jeb3.display= 'block';
  else jeb3.display= 'none';
}