function Main(input) {
    input = input.split("\n");
    var a = parseInt(input[0]);
    var nums = input[1].split(' ').map(Number).sort((a,b) => a-b);
    var b = (nums[0] + nums[1])/2;
    for(var i=2; i<a; i++){
        b = (b + nums[i])/2;
    }
    console.log(b);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
