body{font-family:Arial,sans-serif}.container{max-width:400px;margin:0 auto;padding:20px;border:1px solid #ccc;border-radius:5px}label{display:block;margin-bottom:10px}input[type="number"]{width:100%;padding:5px;margin-bottom:10px}button{background-color:#007bff;color:#fff;padding:10px 20px;border:none;border-radius:5px;cursor:pointer}#result{margin-top:10px;font-weight:700}