.drop {
  display: inline-block;
  width: 150px;
  height: 30px;
  position: relative;
  color: #fff;
}

.drop p {
  display: block;
  width: 100%;
  height: 30px;
  line-height: 30px;
  margin: 0;
  padding: 0 10px;
  box-sizing: border-box;
  background: gray;
}

.drop .dropdown_block {
  display: none;
  width: 100%;
  position: absolute;
  top: 30px;
  left: 0;
  right: 0;
}

.drop:hover .dropdown_block,
.dropdown_block:hover {
  display: block;
}

.drop ul {
  display: block;
  width: 100%;
  background: gray;
  padding: 0;
  margin: 10px 0 0;
  list-style: none;
  max-height: 190px;
  overflow: hidden auto;
}

.drop li {
  display: lock;
  width: 100%;
  height: 30px;
  line-height: 30px;
  padding: 0 10px;
  box-sizing: border-box;
}

.drop li:hover {
  background: #555;
  cursor: pointer;
}