pre{
position: relative;
padding-left: 50px;
}
pre:before{
background-color: #40a1e9;
color: #fff;
content: "</>";
font-size: 13px;
font-weight: 900;
height: 100%;
line-height: 20px;
padding: 5px;
position: absolute;
left: 0;
top: 0;
z-index: 5;
}