How to make a menu in with uniform blocks?

Question

css

Hello.
I ran into a problem how to make a menu with uniform blocks, i.e. each menu item was evenly distributed across the entire width.
And also, how to make a drop-down menu the entire width of the main block?
In search of one junk ... I did not find anything similar.
https://codepen.io/Timers/pen/JLrzrj

Answer 1

https://codepen.io/anon/pen/OvxqKZ

Answer 2

.menu{
...
display:flex;
width:100%;
}
.menu>li{
flex-grow:1;
}