//April//
  var indexApr = 1;
  displayApril(indexApr);

  function April(n) {
    displayApril(indexApr += n);
    }
  
  function activeApril(n) {
    displayApril(indexApr = n);
    }

  function displayApril(n) {
    var i;
    var allApril = document.getElementsByClassName("image-container-4");
    var allThumbnails = document.getElementsByClassName("top-img-4");

    if (n > allApril.length) {
      indexApr = 1;
      }
    if (n < 1) {
      indexApr = allApril.length;
      }
    for (i = 0; i < allApril.length; i++) {
      allApril[i].style.display = "none";
      }
    for (i = 0; i < allThumbnails.length; i++) {
      allThumbnails[i].className = 
        allThumbnails[i].className.replace(" current-top-img", "");
        allThumbnails[i].style.filter = "brightness(50%)";
        }
      if ((indexApr - 1) >= allApril.length || (indexApr - 1) >= allThumbnails.length)
        return;
      allApril[indexApr - 1].style.display = "block";
      allThumbnails[indexApr - 1].className += " current-top-img";
      allThumbnails[indexApr - 1].style.filter = "brightness(100%)";
      }