.dropdown-submenu {
    position: relative;
}

.dropdown-submenu > .dropdown-menu {
    top: 0;
    left: 100%;
    margin-top: -6px;
    margin-left: -2px;
}

.dropdown-submenu:hover > .dropdown-menu {
    display: block;
}

.dropdown-submenu > a:after {
    content: "";
    margin-top: 6px;
    margin-right: -10px;
    float: right;
    border-left: 4px solid;
    border-top: 4px solid transparent;
    border-bottom: 4px solid transparent;
}