Подстветка input. Jquery

$(document).ready(function() { 
  $("#boughtamount").keyup(function() { 
    var value = this.value; 
    var price = 0; 
    if (value > 100) { 
      price = parseInt(value) * 1.25; 
      $("#boughtamount").addClass("selectedgood"); 
 
    } else 
      $("#boughtamount").addClass("selected"); 
    $('.res_sum').text(price); 
  }); 
});

.selected { 
  border: 1px solid red 
} 
 
.selectedgood { 
  border: 1px solid green 
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
<form> 
  <input type="number" placeholder="От 100 монет" id="boughtamount"> 
</form> 
<div class="toPay"> 
  <p><i>К оплате:</i></p> 
</div> 
<div class="finalpriceforitem"> 
  <b><span class="res_sum">0</span>&nbsp;руб.</b> 
</div>