#include <bits/stdc++.h>
int main() {
  int n;
  double sum = 0;
  int a, b;
  int v[1001];
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &v[i]);
  }
  for (int j = 0; j < n - 1; j++) {
    for (int i = 0; i < n - 1; i++) {
      if (v[i] >= v[i + 1]) {
        a = v[i];
        b = v[i + 1];
        v[i] = b;
        v[i + 1] = a;
      }
    }
  }
  sum = (v[0] + v[1]) / 2;
  for (int k = 1; k < n - 1; k++) {
    sum = (sum + v[k + 1]) / 2;
  }
  printf("%lf\n", sum);
  return 0;
}
