body{
    background-color: #404040;
}
div{
    position: relative;
}
.jeden{
    height: 1000px;
    width: 500px;
    position: absolute;
}
.dwa{
    height: 1000px;
    width: 500px;
    position: absolute;
    z-index: 1;
}
.trzy{
    height: 1000px;
    width: 500px;
    position: absolute;
}
.cztery{
    height: 1000px;
    width: 500px;
    position: absolute;
}