#contenedor {
    text-align: center;
}

input[type=text] {
    width: 75%;
    padding: 16px 32px;
    font-size: 16px;
    margin: 8px 0;
    border: 1px solid silver;
    border-radius: 1px;
    text-align: left;
    color: #333;
    background: #ccc;
    text-align: right;
  }

button {
    background-color: #334fff;
    border: none;
    color: white;
    padding: 16px 32px;
    font-size: 20px;
    text-decoration: none;
    margin: 4px 2px;
    cursor: pointer;
    border-radius: 25px;
  }

#normal {
    min-width: 10%;
  }

#sumar, #restar, #multiplicar, #dividir, #elevado {
    min-width: 30%;
    background-color: red;
  }

#sumatorio, #producto {
    min-width: 40%;
    background-color: green;
  }