let drop;
function initiate() {
  const images = document.querySelectorAll("#picturesbox > img");
  for (let i = 0; i < images.length; i++) {
    images[i].addEventListener("dragstart", dragged);
  }
  drop = document.getElementById("dropbox");
  drop.addEventListener("dragenter", function(event) {
    event.preventDefault();
  });
  drop.addEventListener("dragover", function(event) {
    event.preventDefault();
  });
  drop.addEventListener("drop", dropped);
}
function dragged(event) {
  const element = event.target;
  event.dataTransfer.setData("Text", element.id);
}
function dropped(event) {
  event.preventDefault();
  const id = event.dataTransfer.getData("Text");
  if (id != "image4") {
    const src = document.getElementById(id).src;
    drop.innerHTML = '<img src="' + src + '">';
  } else {
    drop.innerHTML = "Not admitted";
  }
}
window.addEventListener("DOMContentLoaded", initiate);