.slider {
  width: 100%;
  margin: auto;
  overflow: hidden;
  line-height:0px;
  
}

.slider ul {
  display: flex;
  padding: 0;
  width: 300%;

  animation: cambio 12s infinite;
  animation-direction: alternate;
  animation-timing-function: linear;
}

.slider li {

  width: 100%;
  list-style: none;
}
.slider img {
  width: 100%;

}

@keyframes cambio {
  0% { margin-left: 0;}
  30% { margin-left: 0;}

  35% { margin-left: -100%;}
  65% { margin-left: -100%;}

  70% { margin-left: -200%;}
  100% { margin-left: -200%;}
  
}