#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (1) {
    scanf("%d", &n);
    double ara[n + 1];
    int j = 1, i;
    for (i = 0; i < n; i++) cin >> ara[i];
    sort(ara, ara + n);
    for (i = 0; i < n; i++) {
      ara[i + 1] = (ara[i] + ara[i + 1]) / 2;
    }
    cout << ara[i - 1] << endl;
  }
}
