/** #cf {
  position:relative;
  margin: 0 0 0 10%;
}

#cf img {
  position:absolute;
  left:0;
  -webkit-transition: opacity .5s ease-in-out;
  -moz-transition: opacity .5s ease-in-out;
  -o-transition: opacity .5s ease-in-out;
  transition: opacity .5s ease-in-out;
}

#cf img.top:hover {
  opacity:0;
} **/


.pic img:last-child{
    display:none;
}

.pic:hover img:first-child{
    display:none;
}

.pic:hover img:last-child{
    display:inline-block   
;}