function changeBg(jmeno) {
        
        newImage = "none";
        show = "visible";
        document.getElementById(jmeno).style.backgroundImage = newImage;
        document.getElementById('p-'+jmeno+'-1').style.visibility = show;
        document.getElementById('p-'+jmeno+'-2').style.visibility = show;
        document.getElementById('p-'+jmeno+'-3').style.visibility = show;
      }
      function backBg(jmeno) {
        newImage = "url(img/"+jmeno+".jpg)";
        show = "hidden";
        document.getElementById(jmeno).style.backgroundImage = newImage;
        document.getElementById('p-'+jmeno+'-1').style.visibility = show;
        document.getElementById('p-'+jmeno+'-2').style.visibility = show;
        document.getElementById('p-'+jmeno+'-3').style.visibility = show;
      }