.slider-box {
  width: 100%;
  height: 450px;
  margin: 50px auto 0;
  overflow: hidden;
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.7);
  border-bottom: rgba(0, 0, 0, .9);
}
.slider-box ul {

  display: flex;
  padding: 0;
  width: 400%;
  animation: slide 20s infinite alternate ease-in-out;
}
.slider-box li {
  width: 100%;
  list-style: none;
  position: relative;
}
.slider-box img {
  width: 100%;
  height: 100%;
  
}
@media (max-width: 950px) {
  .slider-box {
    height: 250px;
    margin: 20px auto 0;
  }
}
@keyframes slide {
  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%;
  }
}