#include <bits/stdc++.h>
int main(void) {
  int i, j, n, tmp, v[n];
  double result = 0;
  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; j++) {
      if (v[i] > v[j]) {
        tmp = v[i];
        v[i] = v[j];
        v[j] = tmp;
      }
    }
  }
  result = (v[0] + v[1]) / 2;
  for (i = 2; i < n; i++) {
    result = (result + v[i]) / 2;
  }
  printf("%lf\n", result);
  return 0;
}
