function Main(input) {
	input = input.split("\n");
	var count = input[0]-0;
  var values = input[1].split(" ");
  
	for(var i = 0; i < count; i++) values[i] = values[i] - 0;
  
  values.sort(function(a,b){ return a - b; });
  
  var previous = values[0];
	for(var i = 1; i < count; i++) {
		previous = (previous + values[i]) / 2;
	}
	console.log(previous);
}

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