Place the arrows to move them over the carousel

Good

I had to place the carousel arrows to change the picture above the carousel as follows:

Enter image description here

I've already used the z-index and tried to change the ad, but it's not over the image.

Here is my code:

var slideIndex = 1;
showDivs(slideIndex);

function plusDivs(n) {
  showDivs(slideIndex += n);
}

function showDivs(n) {
  var i;
  var x = document.getElementsByClassName("mySlides");
  if (n > x.length) {slideIndex = 1}
  if (n < 1) {slideIndex = x.length}
  for (i = 0; i < x.length; i++) {
    x(i).style.display = "none";  
  }
  x(slideIndex-1).style.display = "block";  
}
.mySlides {
    display: none;
    width: 100%;
}

.botao {
    z-index: 2;
    position: inherit;
    display: 
}

.slideshow {
    z-index: -1;
}



Lis River