.slider{
    width: 70%;
    margin: auto;
    overflow: hidden;
}
@media (max-width: 1200px) {
    .slider{
        width: 100%;
        margin: auto;
        overflow: hidden;
    }
}
.slider ul{
    display: flex;
    padding: 0;
    width: 400%;

    animation: cambio 20s infinite alternate linear;
}

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

.slider img{
    width: 100%;
    height: 100%;
    object-fit: cover;
}
@media (max-width: 540px) {
    .slider img{
        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%;}
}