.calculator {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 5px;
    margin: 10px;
    padding: 10px;
}
.calculator input {
    grid-column: span 4;
    text-align: right;
    padding: 10px;
    font-size: 18px;
}
.calculator button {
    padding: 10px;
    font-size: 18px;
}