#include <bits/stdc++.h>
using namespace std;
int main() {
  const int MAX_N = 50;
  const int MAX_V = 1000;
  const float USED = -100.0f;
  int n;
  cin >> n;
  float v[MAX_N];
  for (int i = 0; i < n; i++) cin >> v[i];
  float answer = 0;
  for (int h = 0; h < n - 1; h++) {
    int minDiff = MAX_V;
    int useID[] = {-1, -1};
    int minVal = MAX_V;
    int secondMinVal = MAX_V;
    for (int i = 0; i < n; i++) {
      if (v[i] == USED) continue;
      if (v[i] < minVal) {
        minVal = v[i];
        useID[1] = useID[0];
        useID[0] = i;
      } else if (v[i] < secondMinVal) {
        secondMinVal = v[i];
        useID[1] = i;
      }
    }
    v[useID[0]] = ((v[useID[0]] + v[useID[1]]) / 2);
    v[useID[1]] = USED;
    answer = v[useID[0]];
  }
  cout << answer;
  return 0;
}
