#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  float v[N];
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  float first = 0;
  float second = 0;
  sort(v, v + N);
  while (v[1] != 1000) {
    first = v[0];
    second = v[1];
    v[0] = (first + second) / 2;
    v[1] = 1000;
    sort(v, v + N);
  }
  float ans = v[0];
  cout << ans << endl;
  return 0;
}
