JSFiddle - React, Tailwind, and code Playground

HTML

<div class="form-group">
  <input type="text" placeholder="+7911 111 11 11">
  <button type="button">Получить код</button>
</div>

CSS

.form-group{
  position: relative;
  display: inline-block;
}

.form-group input{
  padding: 10px 120px 10px 5px;
  border: 1px solid #ccc;
  border-radius: 5px;
}

.form-group button{
  position: absolute;
  right: 0;
  top: 7px;
  background-color: transparent;
  border-width: 0;
  border-left: 1px solid #ccc;
  font-weight: bold;
  color: #ccc;
  padding: 3px 10px;
  cursor: pointer;
}