'use strict'

function Main(input) {
  const N = Number(input.split("\n")[0])
  const vList = input.split("\n")[1].split(" ").map(x => Number(x)).sort((a, b) => a - b)

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

  console.log(ans)
}
Main(require("fs").readFileSync("/dev/stdin", "utf8").trim())
