#include <bits/stdc++.h>
int main() {
  int a, count;
  int buf[50] = {0};
  scanf("%d", &count);
  for (int i = 0; i < count; i++) {
    scanf("%d", &buf[i]);
  }
  double tmp = 0;
  for (int i = 0; i < count - 1; i++) {
    if (buf[i] < buf[i + 1]) {
      tmp = buf[i + 1];
      buf[i + 1] = buf[i];
      buf[i] = tmp;
    }
  }
  for (int i = count - 1; i >= 0; i--) {
    buf[i - 1] = (buf[i - 1] + buf[i]) / 2;
  }
  printf("%lf", (double)buf[0]);
  return 0;
}
