#include <bits/stdc++.h>
int main(void) {
  int N;
  scanf("%d", &N);
  int v[N];
  double result = 0;
  for (int i = 0; i < N; i++) scanf("%d", &v[i]);
  for (int i = 0; i < N - 1; i++) {
    for (int j = i + 1; j < N; j++) {
      if (v[i] > v[j]) {
        int t = v[j];
        v[j] = v[i];
        v[i] = t;
      }
    }
  }
  result = (v[0] + v[1]) / 2.0;
  for (int i = 2; i < N; i++) result = (result + v[2]) / 2.0;
  printf("%f", result);
  return 0;
}
