.slider {
    width: 100%;
    margin: auto;
    overflow: hidden;
}

.slider ul {
    display: flex;
    padding: 0;
    width: 800%;

    animation: cambio 40s infinite;
    animation-direction: alternate;
    animation-timing-function: linear;
}

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

@keyframes cambio{
    0%  {margin-left: 0;}
    10% {margin-left: 0;}

    12.5% {margin-left: -100%;}
    22.5% {margin-left: -100%;}

    25% {margin-left: -200%;}
    35% {margin-left: -200%;}

    37.5%  {margin-left: -300%;}
    47.5% {margin-left: -300%;}

    50%  {margin-left: -400%;}
    60% {margin-left: -400%;}

    62.5% {margin-left: -500%;}
    72.5% {margin-left: -500%;}

    75% {margin-left: -600%;}
    85% {margin-left: -600%;}

    87.5% {margin-left: -700%;}
    100% {margin-left: -700%;} 
}