input {
  width: calc(100% - 8px); /* 8px to account for the default padding and border */
}
.tag {
  float: right;
  margin-left: 1em;
  font-size: 80%;
}
span.tag {
  color: white;
  padding: 1px .5em;
  font-weight: bold;
}
input.tag {
  width: 7em;
  border: none;
}