#include <bits/stdc++.h>
int main(void) {
  int n;
  scanf("%d", &n);
  double a[n];
  for (int i = 0; i < n; i++) {
    scanf("%lf", &a[i]);
  }
  int iidx, jidx, min = 1000, c = 0;
  while (c < n - 1) {
    for (int i = 0; i < n - 1; i++) {
      for (int j = i + 1; j < n; j++) {
        if (a[j] == 0) continue;
        if (a[i] == 0) continue;
        if (abs(a[i] - a[j]) < min) {
          min = abs(a[i] - a[j]);
          iidx = i;
          jidx = j;
        }
      }
    }
    a[iidx] = (a[iidx] + a[jidx]) / 2;
    a[jidx] = 0;
    c++;
    min = 1000;
  }
  printf("%lf", a[iidx]);
  return 0;
}
