function Main(input) {
  lines = input.split('\n')
  N = lines[0] * 1
  s = lines[1].split(" ").map(function(a) { return a * 1 }).sort(function(a, b) { return a - b }) 
  f = s.shift()
  ans = s.reduce(function(i, a) {
      return (i + a) / 2
  }, f)
  console.log(ans)
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"))