#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  std::priority_queue<float, std::vector<float>, std::greater<float>> q;
  for (int i = 0; i < n; i++) {
    float v;
    scanf("%f", &v);
    q.push(v);
  }
  while (true) {
    int v1 = q.top();
    q.pop();
    int v2 = q.top();
    q.pop();
    int v3 = (v1 + v2) / 2.0;
    if (q.empty()) {
      cout << v3 << endl;
      break;
    }
    q.push(v3);
  }
}
