*{margin:0;padding:0;   box-sizing: border-box;}
div{padding:50px;}
ul{
   height:40px;
  width:400px;
}
ul li{
 float:left;
  width:100px;
  height:40px;
  line-height:80px;
  border-bottom:1px solid #ccc;
  text-align: center;
  list-style:none; 
}

ul li:first-child{
   border-left:1px solid #ccc;
}
ul:nth-child(2n) li{
 float:right
}
ul:nth-child(2n) li:first-child{
 border-right:1px solid #ccc;
  border-left:none;
}