#include <bits/stdc++.h>
void quick(float array[], int left, int right) {
  int pl = left, pr = right;
  float x = array[(left + right) / 2];
  do {
    while (array[pl] < x) pl++;
    while (array[pr] > x) pr--;
    if (pl <= pr) {
      do {
        float t = array[pl];
        array[pl] = array[pr];
        array[pr] = t;
      } while (0);
      pl++, pr--;
    }
  } while (pl <= pr);
  if (pl < right) quick(array, pl, right);
  if (pr > left) quick(array, left, pr);
}
int main() {
  int n;
  scanf("%d", &n);
  float v[52];
  for (int i = 0; i < n; i++) scanf("%f", &v[i]);
  while (n > 1) {
    quick(v, 0, n - 1);
    v[0] = (v[0] + v[n - 1]) / 2;
    n = n - 1;
  }
  printf("%f\n", v[0]);
  return 0;
}
