*{
margin:0;
padding:0;
box-sizing: border-box;
}

.slider{
width:100%;
height:60%;
overflow: hidden;
}

.slider ul{
display: flex;
animation: cambio 20s infinite alternate linear;
width:400%;
}

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

.slider img{
width:100%;
height:100%;
}

@keyframes cambio{
0%{margin-left:0;}
20%{margin-left: 0;}

25% {margin-left:-100%;}
45% {margin-left:-100%;}

50% {margin-left:-200%;}
70% {margin-left:-200%;}

75% {margin-left:-300%;}
100% {margin-left:-300%;}
}