function showAdditional() {
  document.getElementById('additional_show').style.display == 'block' ? (document.getElementById('additional_show').style.display = "none") : (document.getElementById('additional_show').style.display = "block");
  document.getElementById('additional_text').style.display == 'none' ? (document.getElementById('additional_text').style.display = "block")  : (document.getElementById('additional_text').style.display = "none");
}
function newImage(path) {
  var image = new Image();
  image.src = path;
  return image;
}
function preImg() {
  img1 = newImage("../i/bg_man_1.jpg");
  img2 = newImage("../i/bg_man_2.jpg");
  img3 = newImage("../i/bg_man_3.jpg");
  img4 = newImage("../i/bg_man_4.jpg");
  img5 = newImage("../i/bg_man_5.jpg");
}