function gallery(galleryid, arrow, stringid, photo_number) {
if (stringid == null && photo == null) {
var gallery = galleryid.parentElement.parentElement.getElementsByTagName('*');
photo_number = 0;
}else{
var gallery = document.getElementById(stringid).getElementsByTagName('*');
photo_number -= 1;
}

var type;
for (var i = 0; i < gallery.length; i++) {
if (gallery[i].id == "gallery_photo") {
var photo = gallery[i];
var photo2 = gallery[i].getElementsByTagName('img')[0];
type = "";
if (photo.hasAttribute("type")) {
type = photo.getAttribute("type");
}
}
if (gallery[i].id == "counter") {
var counter = gallery[i];
}
if (gallery[i].id == "counter_all") {
var counter_all = gallery[i];
}
if (gallery[i].id == "gallery_photos") {
var gallery_photos = gallery[i];
}
}
var photos = gallery_photos.getElementsByTagName('img');
if (type == "" || type == "img") {
photo.setAttribute("style", "background-image: url("+photos[photo_number].src+")");
}
if (type == "doc") {
photo2.setAttribute("src", photos[photo_number].src);
}
var photo_max = photos.length;


if (stringid != null && photo != null) {
counter.innerHTML = photo_number + 1;
}


var gallery_count = Number(counter.innerHTML) -1;


if (arrow == "left") {
gallery_count -= 1;
}

if (arrow == "right" && gallery_count != photo_max) {
gallery_count += 1;
}

if (arrow == "left" && gallery_count == -1) {
gallery_count = photo_max-1;
}

if (arrow == "right" && gallery_count == photo_max) {
gallery_count = 0;
}



if (arrow == "left" && gallery_count != 0 || arrow == "right" && gallery_count != photo_max) {
if (type == "" || type == "img") {
photo.setAttribute("style", "background-image: url("+photos[gallery_count].src+")");
}
if (type == "doc") {
photo2.setAttribute("src", photos[gallery_count].src);
}
}
counter_all.innerHTML =  photo_max;
counter.innerHTML = gallery_count+1;
}