"use strict"

const main = (input) => {
    const _input = input.split("\n");
    const v = _input[1].split(" ").map(e => parseInt(e)).sort((a, b) => a - b);
    
    let result = (v[0] + v[1])/2;
    for(let i = 2; i < v.length; i++){
        result = (result + v[2])/2;
    }
    console.log(result);
}

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