#include <bits/stdc++.h>
int main(void) {
  int N, i, j, v[55], temp;
  double ans;
  scanf("%d", &N);
  for (i = 0; i < N; i++) {
    scanf("%d", &v[i]);
  }
  for (i = 0; i <= N; i++) {
    for (j = i + 1; j <= N - 1; j++) {
      if (v[i] > v[j]) {
        temp = v[i];
        v[i] = v[j];
        v[j] = temp;
      }
    }
  }
  ans = (v[0] + v[1]) / 2;
  if (N >= 3) {
    for (i = 2; i <= N - 1; i++) {
      ans = (ans + v[i]) / 2;
    }
  }
  printf("%lf", ans);
}
