function Main(input) {
	input = input.split("\n");
	tmp = input[0].split(" ");
	var number = input[1].split(" ");
	var answer = 0;
	number.sort(
      function(a,b){
        return (a < b ? -1 : 1);
      }
    );
	answer = Number(number[0]);
	for(var i=1;i<tmp;i++){
      answer = (answer+Number(number[i]))/2;
    }
	console.log(answer);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));