.slider {
    width: 100%;
    margin:auto;
    overflow: hidden;
}
.slider ul {
    display: flex;
    padding: 0; 
    width: 800%;
    
    animation: cambio 20s infinite;
    animation-direction: alternate;
    animation-timing-function: step-start;
}
.slider li{
    width: 100%;
    list-style: none;
}

.slider img {
    width: 400px;
    height: 400px;
    border-radius: 10% ;
    border: 7px solid #fff;
    margin-left: auto;
    margin-right: auto;
   
}
@keyframes cambio {
    0% {margin-left: 0;}
    13% {margin-left: 0;}
    
    15% {margin-left: -100%;}
    28% {margin-left: -100%;}
    
    30% {margin-left: -200%;}
    43% {margin-left: -200%;}
    
    45% {margin-left: -300%;}
    58% {margin-left: -300%;}
    
    60% {margin-left: -400%;}
    73% {margin-left: -400%;}
    
    75% {margin-left: -500%;}
    88% {margin-left: -500%;}
    
    90% {margin-left: -600%;}
    100% {margin-left: -600%;}
    
   
}