CSS悬停不会影响其他元素

CSS :hover在我使用它自己的元素时起作用,但是当我试图影响另一个元素时,它没有任何效果.

例如,当我将鼠标悬停在此按钮时,隐藏的链接应该出现,但它们不会出现.

.dropdown {
  position: relative;
  display: inline-block;
  border: 1px solid black;
  width: 200px;
}
.dropbutton {
  width: 100%;
  height: 60px;
  color: white;
  background: #017678;
  border: none;
}
.dropcontent a {
  color: black;
  text-align: center;
  line-height: 40px;
  text-decoration: none;
  height: 40px;
  background-color: #DDD;
  border-width: 0 0 1px 0;
  border-style: solid;
  border-color: #9fa0a8;
  display: none;
}
a:last-of-type {
  border: none;
}
.dropbutton:hover .dropcontent {
  display: block;
}

  SHOW CONTENT
  

    c1
    c2
    c3
  

.dropbutton:hover + .dropcontent a {