* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            position: relative;
        }

        ul,
        li {
            list-style: none;
        }

        .nav_1st {
            width: 500px;
            height: 30px;
            line-height: 20px;
            padding: 5px 30px 5px 5px;
            border: 1px solid #000;
            background: url(../img/todown.png) no-repeat center right;
            background-size: 5%;
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
            margin: 0 auto;
        }

        .nav {
            width: 500px;
            line-height: 30px;
            border: 1px solid #000;
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
            position: absolute;
            top: 30px;
            right: 0;
            left: 0;
            margin: auto;
            z-index: 9999;
            display: none;
        }

        .nav_close {
            position: fixed;
            top: 0;
            bottom: 0;
            left: 0;
            right: 0;
            z-index: 9990;
            display: none;
        }

        .nav li input {
            margin: 0 5px;
        }

        .nav li p:hover {
            background: #1e90ff;
            color: #fff;
        }

        .nav-2nd {
            padding-left: 37px;
        }

        #classification {
            white-space: nowrap;
            overflow: hidden;
            text-overflow: ellipsis;
        }