body,html{
    background-color:white;
}
.contenedor{
    position: relative;
    top: 2px;
    width: 96%;
    height: auto;
    margin: auto;
    overflow: hidden;
    border: 2px solid #aaa;
}
.contenedor ul{
    display: flex;
    padding:0;
    width:400%;
    animation: cambio 15s infinite;
}
.contenedor li{
    width:100%;
    list-style:none;
}
.contenedor img{
    width:100%;
    
}
    
    @keyframes cambio{
        0%,20%{margin-left: 0px;}
       25%,45%{margin-left: -100%;}
       50%,70%{margin-left: -200%;}
       75%,100%{margin-left: -300%;}
        
    }