.wrapper {
    width: 500px;
    height: 1500px;
    border: 3px solid black;
}

.box-1 {
    background-color: green;
    height: 50px;
}

.box-2 {
    background-color: red;
    height: 50px;
}

.box-3 {
    background-color: blue;
    height: 50px;
}