.box {
    display: flex;
    align-items: center;
    justify-content: center;
}
.box .form-control {
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
}
.box .btn {
    border-top-left-radius: 0;
    border-bottom-left-radius: 0;
    color: white;
}
.box .btn:hover {
    background-color: black;
    color: white;
}
.box .btn:focus {
    box-shadow: 0 0 0 0.25rem rgba(0, 0, 0, 0.25);
}