*{
    box-sizing: border-box;
}

header,footer{
    height: 150px;
    border: 3px solid black;
    clear: both;
}

.long{
    border: 3px solid pink;
    float: left;
    height: 300px;
    width: 100%;
    clear: both;
}

.short{
    border: 3px solid orange;
    height: 300px;
    float: left;
    width: 35%;
    position: relative;
}

.medium{
    border: 3px solid brown;
    height: 300px;
    float: right;
    width: 65%;
    position: relative;
    
}