"use strict";
main(require("fs").readFileSync("/dev/stdin", "UTF-8"));

function main(input) {
  input = input.split("\n");
  let N = parseInt(input.shift());
  input = input[0]
    .split(" ")
    .map(n => parseInt(n))
    .sort();
  while (input.length >= 3) {
    let i = 0;
    input[i] = (input[i] + input[i + 1]) / 2;
    input.splice(i + 1, 1);
  }
  console.log((input[0] + input[input.length - 1]) / 2);
}
