input {
  width:300px;
  height:38px;
  text-align:center;
}

#bttn {
  padding : 10px 20px;
  border-style: 1px solid #ccc;  
}

#result {
  margin-top:50px;
  padding:15px 20px;
  background-color:azure;
  text-align:center;
  font-size:2.5em;
  font-weight: bold;
}