that's my problem:
I have a list of things in a flex container and they are divided by a separator like is shown in the screen below
Problem is, when you resize the window and make it smaller, they go on different rows and I'd like to get rid of the separator that is in the last part of the row, so that the rest is well centered.

By the way I tried to use margins to make the separators, but then I had problem centering them on every size of the div.
Any hint how to accomplish that with css?
That's the code I have now
@import "compass/css3";
.flex-container {
padding: 0;
margin: 0;
list-style: none;
display: -webkit-box;
display: -moz-box;
display: -ms-flexbox;
display: -webkit-flex;
display: flex;
-webkit-flex-flow: row wrap;
justify-content: space-around;
align-items: center;
}
.flex-item {
padding: 5px;
margin-top: 10px;
min-width:100px;
line-height: 150px;
color: blaclk;
font-weight: bold;
font-size: 1.5em;
text-align: center;
opacity: 0.7;
}
.flex-item img{
width: 100%;
}
.separator{
background: rgb(127, 0, 0);
background: rgba(192,192,192,.5);
width: 1px;
height: 100px;
}
<div class="flex-container">
<div class="flex-item " ><center><p> 1 </p></center></div>
<div class="separator"></div>
<div class="flex-item " ><center><p> 2 </p></center></div>
<div class="separator"></div>
<div class="flex-item " ><center><p> 3 </p></center></div>
<div class="separator"></div>
<div class="flex-item " ><center><p> 4 </p></center></div>
</div>