function Main(input) {
	var list = input.split("\n")[1].split(" ");
   var output = 0;
  for(var i = 0; i < list.length; i++){
    list[i] = parseInt(list[i]);
  }
  list.sort(function(a,b){
  	return a - b;
  });
  while(list.length != 1){
    var x = list[0];
    var y = list[1];
    var make = (x + y) / 2;
    list.shift();
    list[0] = make;
  }
  console.log(list[0]);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));
