导航栏覆盖问题

Question

当我缩小屏幕时，导航栏中的搜索栏会在导航栏上滑动。

如何使其停止在导航链接上滑动？

.topnav {
  width: 100%;
  opacity: 1;
  background-color: rgba(255, 255, 255, 0.6);
  margin-bottom: 10px;
  padding: 5px 0px 5px 0;
  border-bottom: dotted #66A761;
  border-top: dotted #66A761;
  position: relative;
  text-align: center;
}

.topnav ul {
  display: inline;
  text-align: left;
}

.topnav ul li {
  display: inline-block;
  margin: 0 30px;
  padding: 0;
  text-indent: 0;
  position: relative;
  cursor: pointer;
  -webkit-transition: all 0.2s;
  -moz-transition: all 0.2s;
  -ms-transition: all 0.2s;
  -o-transition: all 0.2s;
  transition: all 0.2s;
}

.topnav a {
  font-size: 20px;
  font-weight: bold;
  text-decoration: none;
}

.topnav a:link {
  color: #9F257D;
}

.topnav a:hover {
  color: #66A761;
}

.topnav input {
  float: right;
  padding: 3px;
  margin: 0 5px;
  position: absolute;
  right: 20px;
}

.topnav ul li ul {
  display: block;
  position: absolute;
  background-color: rgba(255, 255, 255, 0.6);
  padding: 5px 5px;
}

.topnav ul li:hover ul li {
  display: block;
  z-index: 1;
}

.topnav ul li ul li {
  display: none;
}

<div class="topnav">
  <nav>
    <ul>
      <li><a href="recepten.html">recepten</a>
        <ul>
          <li><a href="lactosevrij.html">lactosevrij</a></li>
          <li><a href="suikervrij.html">suikervrij</a></li>
          <li><a href="glutenvrij.html">glutenvrij</a></li>
        </ul>
      </li>
      <li><a href="varianten.html">varianten</a>
        <ul>
          <li><a href="basis1.html">basis</a></li>
          <li><a href="standaard1.html">standaard</a></li>
          <li><a href="luxe1.html">luxe</a></li>
        </ul>
      </li>
      <li><a href="contact.html">contact</a></li>
      <li><a href="overons.html">over ons</a></li>
      <input type="text" style="right:0" placeholder="Search..">
    </ul>
  </nav>
</div>