body {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  width: 300px;
  margin-top: 50px;
}

.calculator input {
  width: 100%;
  margin-bottom: 10px;
}

.calculator button {
  margin: 5px;
}