var foo=0
var wid=$('.wrap').width()
var num=$('li').length
$('ul').width(num*100+'%')
$('.prev').on('click',function(){
  foo=slide(--foo,num)
})

$('.next').on('click',function(){
  foo=slide(++foo,num)
})

function slide(n,num){
  if(n>num-1) n=0
  if(n<0) n=num-1
  $('ul').css({
    'margin-left':-n*100+'%'  })
  return n
}

function autoSlide(delay){
  setTimeout(function(){
	  foo=slide(++foo,num)
    autoSlide(delay)
  },delay)
}
autoSlide(2000)