body {
  font-family: sans-serif;
}

.calculator {
  margin: 20px auto;
  width: 400px;
  border: 1px solid #ccc;
  padding: 20px;
  border-radius: 5px;
}

label {
  display: block;
  margin-bottom: 5px;
}

input[type="number"] {
  width: 100%;
  padding: 10px;
  border: 1px solid #ccc;
  border-radius: 3px;
}

button {
  background-color: #4CAF50;
  color: white;
  padding: 10px 20px;
  border: none;
  border-radius: 3px;
  cursor: pointer;
  margin-top: 10px;
}

button:hover {
  background-color: #3e8e41;
}

#result {
  margin-top: 10px;
  font-weight: bold;
}