#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long int exp(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  int n;
  cin >> n;
  double x[n];
  double sum;
  for (int i = 0, _n = (n); i < _n; i++) {
    cin >> x[i];
  }
  sort(x, x + n);
  sum = (x[0] + x[1]) / 2;
  for (int i = (2), _b = (n - 1); i <= _b; i++) {
    sum = (sum + x[i]) / 2;
  }
  printf("%0.1f", sum);
  return 0;
}
