*{
                margin: 0;
                padding: 0;
            }
            ul,li{
                list-style: none;
            }
            .ui-slide-box{
                width: 300px;
            }
            .ui-slide-item{
                width: 100%;
                position: relative;
            }
            .ui-slide-item-text{
                display: block;
                background-color: #000000;
                color: white;
                border-bottom: 1px solid yellow;
                height: 40px;
                line-height: 40px;
            }
            .ui-slide-item .ui-slide-box{
                display: none;
                position: absolute;
                left: 300px;
                top: 0;
            }
            .ui-slide-item:hover > .ui-slide-box{
                display: block;
            }

<ul class="ui-slide-box">
            <li class="ui-slide-item">
                <span class="ui-slide-item-text">aaaaaaaaaaaaa</span>
                <ul class="ui-slide-box">
                    <li class="ui-slide-item">
                        <span class="ui-slide-item-text">aaaaaaaaaaaa</span>
                        <ul class="ui-slide-box">
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">dddddddd </span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">sssssssssssss</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">eeeeeeeeeeee</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">ccccccccccccc</span>
                                <ul class="ui-slide-box">
                                    <li class="ui-slide-item">
                                        <span class="ui-slide-item-text">aaaaaaaaaaaaa</span>
                                        <ul class="ui-slide-box">
                                            <li class="ui-slide-item">
                                                <span class="ui-slide-item-text">aaaaaaaaaaaa</span>
                                                <ul class="ui-slide-box">
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">dddddddd </span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">sssssssssssss</span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">eeeeeeeeeeee</span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">ccccccccccccc</span>
                                                    </li>
                                                </ul>
                                            </li>
                                            
                                            <li class="ui-slide-item">
                                                <span class="ui-slide-item-text">bbbbbbbbbb</span>
                                                <ul class="ui-slide-box">
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">sfsdfsdfsd </span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">cvwdfsd</span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">ewewewe</span>
                                                    </li>
                                                    <li class="ui-slide-item">
                                                        <span class="ui-slide-item-text">xxcxc</span>
                                                    </li>
                                                </ul>
                                            </li>
                                        </ul>
                                    </li>
                                </ul>
                            </li>
                        </ul>
                    </li>
                    
                    <li class="ui-slide-item">
                        <span class="ui-slide-item-text">bbbbbbbbbb</span>
                        <ul class="ui-slide-box">
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">sfsdfsdfsd </span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">cvwdfsd</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">ewewewe</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">xxcxc</span>
                            </li>
                        </ul>
                    </li>
                </ul>
            </li>
            <li class="ui-slide-item">
                <span class="ui-slide-item-text">bbbbbbbbbbb</span>
                <ul class="ui-slide-box">
                    <li class="ui-slide-item">
                        <span class="ui-slide-item-text">aaaaaaaaaaaa</span>
                        <ul class="ui-slide-box">
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">dddddddd </span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">sssssssssssss</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">eeeeeeeeeeee</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">ccccccccccccc</span>
                            </li>
                        </ul>
                    </li>
                </ul>
            </li>
            <li class="ui-slide-item">
                <span class="ui-slide-item-text">cccccccccccccccccc</span>
                <ul class="ui-slide-box">
                    <li class="ui-slide-item">
                        <span class="ui-slide-item-text">rrrrrrrrrrrrrrrrrrrrrrrrrr</span>
                        <ul class="ui-slide-box">
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">dddddddd </span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">sssssssssssss</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">eeeeeeeeeeee</span>
                            </li>
                            <li class="ui-slide-item">
                                <span class="ui-slide-item-text">ccccccccccccc</span>
                            </li>
                        </ul>
                    </li>
                </ul>
            </li>
        </ul>