*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;    
}

body {
    background: blue;
}

div {
    height: 33.33vh;
}

#fahrenheit {
    border-top: 4px solid white;
    border-bottom: 4px solid white;
    
}

input[type=number] {
    width: 100%;
    height: 100%;
    font-family: Verdana, Tahoma, sans-serif;
    background: blue;
    color: white;
    font-size: 8em;
    text-align: center;
    border: 0;
}