* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
    border: 0;
}

nav {
    width: 100%;
    display: flex;
    justify-content: space-between;

}

nav>* {
    flex: 1;
}


ul {
    list-style: none;
}

li {
    display: block;
    width: 100%;
}

#ul0 {
    padding: 0;
    display: flex;
    text-align: center;
}

#ul0>li {
    display: block;
}

.sub {
    display: none;
}

li:hover>.sub {
    display: block;
}