.menu-chinh {
    list-style: none;
    padding: 0;
    margin: 0;
    background-color: blue;
    display: flex;
    font-family: Arial, sans-serif;
}

.menu-chinh > li {
    position: relative;
    border-right: 1px solid white;
}

.menu-chinh > li > a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 15px 30px;
    text-align: center;
}

.menu-chinh > li > a:hover {
    background-color: oldlace;
    color: blue;
}


.menu-doc {
    display: none;
    position: absolute;
    list-style: none;
    padding: 0;
    margin: 0;
    width: 200px;
    background-color: blue;
    top: 100%;
    left: 0;
    z-index: 10;
}

.menu-doc li {
    border-bottom: 1px solid white;
}

.menu-doc li a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 10px 15px;
}

.menu-doc li a:hover {
    background-color: oldlace;
    color: blue;
}


.submenu:hover .menu-doc {
    display: block;
}