CSS Slideshow With Fade In/out Delay

I made an CSS slideshow with 3 images animated by keyframes that makes a fade in/out effect. So far, so well. But there's a problem with the animation on the second loop of the sli

Solution 1:

    .imgbox{
  display: flex; 
  align-items: center;
  height: 100%;
  width: 100%;
  background-position: center center;
  background-size: cover; 
}

#img1{
  position: absolute;
  z-index: 3;
  animation: xfade 15s -0s infinite;
  animation-timing-function: ease-in-out;
}

#img2{
  position: absolute;
  z-index: 2;
  animation: xfade 15s -5s infinite;
  animation-timing-function: ease-in-out;
}

#img3{
  position: absolute;
  z-index: 1;
  animation: xfade 15s -10s infinite;
  animation-timing-function: ease-in-out;
}

@keyframes xfade{

     0% {opacity: 0;}
    20% {opacity: 1;}
    33% {opacity: 1;}
    53% {opacity: 0;}
    100% {opacity: 0;}
}

I just set up a jsfiddle with an updated version for you. https://jsfiddle.net/87axbx1o/ Let me know if that works well for you