const main = (input) => {
  var a = input[0]-0;
  var b = input[1].split(" ").map(v=>v-0).sort((a,b)=>a-b);
  var ans = 0;
  for(var i=0;i<a-1;i++){
    b[i+1] = (b[i] + b[i+1])/2;
  }
  console.log(b[a-1]);
}

main(require('fs').readFileSync('/dev/stdin', 'UTF-8').trim().split("\n"));
