var toInt = x=>parseInt(x,10);
var toIntArr = arr=>arr.map(x=>toInt(x));
var abs = x=>x>0?x:-x;
function min(){var rest=arguments,v=rest[0];for(var i=1;i<rest.length;i++)if(rest[i]<v)v=rest[i];return v}
function max(){var rest=arguments,v=rest[0];for(var i=1;i<rest.length;i++)if(rest[i]>v)v=rest[i];return v}
function gcd(){var rest=arguments,v=rest[0],temp=(a,b)=>b?temp(b,a%b):a;for(var i=1;i<rest.length;i++)v=temp(v,rest[i]);return v}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
 
function Main(input){
	var input = input.split('\n').map((el,ind,arr)=>toIntArr(el.split(' ')));
	var n = input[0][0];
	var vs = [];
	for(var i = 0 ; i<n; i++){
		vs.push(input[1][i])
	}
	vs.sort();
	var pows = [1];
	//console.log(n,vs);
	ans = vs[0]+vs[1];
	ans /= 2;
	for(var i = 2; i < n; i++){
		ans += vs[i];
		ans /= 2;
	}
	console.log(ans.toFixed(8));
	return 0;
}
