SOURCE

<div class="container">
    <div class="a"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
</div>

div{
    box-sizing: border-box;
}
.container{
    display: grid;
    grid-template-columns: 100px 100px;
}
.container .item{
    height: 80px;
    border: 5px solid black;
    /* margin-left: -5px;
    margin-top: -5px; */
}

.a{
    height: 80px;
    border: 5px solid red;
    margin-left: -5px;
    margin-top: -5px;
}