flex border-box

ul{ list-style: none; width: 100%; margin: auto;}

.li1{ float: left; background: red; width: 25%; -webkit-box-sizing: border-box; -moz-box-sizing: border-box; box-sizing: border-box; border: 3px solid #000000; text-align: center;}

.list2{ display: flex;}

.li2{ flex: 1; text-align: center;}

.list3{ display: flex; justify-content: space-around;}