#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};
    for (int i = 0; i < n; i++) {
      for (int j = i + 1; j < n; j++) {
        if (v[j] == USED) continue;
        int diff;
        if (v[i] > v[j])
          diff = v[i] - v[j];
        else
          diff = v[j] - v[i];
        if (diff < minDiff) {
          minDiff = diff;
          useID[0] = i;
          useID[1] = j;
        } else if (diff == minDiff) {
          int preBig = v[useID[0]];
          if (v[useID[1]] > preBig) preBig = v[useID[1]];
          int big = v[i];
          if (v[j] > big) big = v[j];
          if (big > preBig) {
            useID[0] = i;
            useID[1] = j;
          }
        }
      }
    }
    v[useID[0]] = ((v[useID[0]] + v[useID[1]]) / 2);
    v[useID[1]] = USED;
    answer = v[useID[0]];
  }
  cout << answer;
  return 0;
}
