"use strict"

function Main(input) {
    const N = parseInt(input[0], 10);
    const V = input.slice(1).map(v => parseInt(v, 10));

    const sortedV = V.sort((a, b) => a - b);
    let result = 0;

    for (let i = 0; i < N - 1; i++) {
        if (i === 0) {
            result = (sortedV[i] + sortedV[i + 1]) / 2;
        } else {
            result = (result + sortedV[i + 1]) / 2;
        }
    }

    console.log(result);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split(/\n|\s/));