#include <bits/stdc++.h>
int main() {
  int n, i, j;
  scanf("%d", &n);
  float v[n];
  for (i = 0; i < n; i++) {
    scanf("%f", &v[i]);
  }
  std::sort(v, v + (sizeof(v) / sizeof(v[0])));
  for (i = 0; i < n - 1; i++) {
    v[i + 1] = (v[i] + v[i + 1]) / 2;
  }
  printf("%f", v[n - 1]);
}
