.modal-backdrop.show 
{
    opacity: 1.0;
    background-color: #000000d6;
}
.modal-header
{
    padding:0
}
.btncustom {
    position: absolute;
    right: 6px;
    top: -8px;
    font-size: 45px;
    color: #000;
    border: 0;
    width: auto;
    height: auto;
    line-height: inherit;
    padding: 0;
    margin: 0;
    z-index: 100;
}
.modal-header-cus {
    padding: 0;
    margin: 0;
    border: 0;
}
.select_st 
{
    background-color: #fff;
    border: 1px solid #ced4da;
    box-shadow: none;
    background-image: url(https://baomatfb.vn/imggg.jpg);
    background-position: right 4px bottom 50%;
    background-repeat: no-repeat;
    padding: 11px;
    width: calc(100% /3 - 7px);
    text-align-last: center;
    font-size: 16px;
}