.a{
    height: 4cqb;
    width: 100%;
    background-color: rgb(241, 238, 238);
    margin-top: 57px;
    }
.nav .b{
    display: none;
       
}
.nav .b{
       height: 100px;
       }

.nav ul li:hover .b{
    display: block;
    position: absolute;
    margin: 0;
    margin-left: 0px;
 
    background-color: rgb(54, 45, 45);;
}
.nav ul li:hover .b ul{
    display: block;
    padding: 10px;

}