How to remove bootstrap grid column space

Question

My code look like that

<div className="row">
<div className="col-6" style={{height:'10rem'}}>
    1
</div>
<div className="col-6" style={{height:'15rem'}}>
    2
</div>
<div className="col-6">
    3
</div>

Now my 1 and 3 has extra 5rem space which I don't need. I want 3 immediately after 1.

I want this layout in bootstrap grid.