.l a {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 10%;
  height: 100%;
}

.l a:hover {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 10%;
  height: 100%;
  background: rgba(0, 51, 102, .5);
}

.r a {
  display: block;
  position: absolute;
  top: 0;
  right: 0;
  width: 10%;
  height: 100%;
}

.r a:hover {
  display: block;
  position: absolute;
  top: 0;
  right: 0;
  width: 10%;
  height: 100%;
  background: rgba(0, 51, 102, .5);
}