使用 CSS 网格布局跨越所有列/行的项目

I've tried to create a simple grid with one item a spanning the left side of all of the rows, with the other items (b, c, d, e, etc.) spanning the right side of individual rows. The amount of items spanning the right side of the rows is variable, so there might be any combination of b, c, d, e, etc., so I'm using the grid-auto-rows property. As such, I cannot define a fixed number of rows for a to span, but I would like a to span all available rows.

#container {
    display: grid;
    grid-auto-flow: column;
    grid-auto-rows: auto;
    grid-template-columns: [left] 4rem [right] 1fr;
    margin: 0rem auto;
    max-width: 32rem;
}
#a {
    background: lightgreen;
    grid-column: left;
    grid-row: 1 / auto;
    justify-self: center;
}
#b {
    grid-area: auto / right;
    background: yellow;
}
#c {
    grid-area: auto / right;
    background: pink;
}
#d {
    grid-area: auto / right;
    background: lightskyblue;
}
#e {
    background: plum;
    grid-area: auto / right;
}

<div id="container">
    <div id="a">a</div>
    <div id="b">b</div>
    <div id="c">c</div>
    <div id="d">d</div>
    <div id="e">e</div>
</div>

我应该怎么做才能使 a 跨越所有行而不知道最终会有多少行?

grid-column: 1/-1;