.big{
    width: 1400px;
    position: relative;
    margin: 0 auto;
}
.pic {
    width: 1400px;
    margin: 0 auto;
    height: 623px;
}
.pic img{
    cursor: pointer;
    position: absolute;/*绝对定位*/
    display: none;
}

.arr{
    width: 40px;
    height: 70px;
    font-size: 30px;
    font-weight: 900;
    line-height: 70px;
    text-align: center;
    color: #ccc;
    position: absolute;
    top: 46%;
    bottom: 10%;
    display: none;
    cursor: pointer;
}
.l-arr{
    left: 50px;
}
.r-arr{
    right: 50px;
}
.big:hover .arr{
    display: block;
}
.arr:hover{
    background: rgba(0,0,0,0.3);
    color: #fff;
}
.but{
    position: absolute;
    bottom: 30px;
    left: 650px;
}
.but ul li{
    list-style-type: none;
    width: 30px;
    height: 20px;
    /*border: 1px solid #ccc;*/
    float: left;
    margin-left: 10px;
    text-align: center;
    font-family: "microsoft yahei";
    line-height: 20px;
    font-size: 12px;
    color: #fff;
    background: rgba(0,0,0,0.3);
    cursor: pointer;
}
.but ul li:hover{
    background:rgba(0,0,0,0.7);
}
.but .hover{
    background:rgba(0,0,0,0.7);
}