#include <bits/stdc++.h>
int main(void) {
  int i, j, k, l;
  double n, v[100], t;
  scanf("%lf", &n);
  for (i = 0; i < n; i++) {
    scanf("%lf", &v[i]);
  }
  for (i = n; i > 1; i--) {
    for (j = 0; j < n; j++) {
      for (k = j + 1; k < n; k++) {
        if (v[j] > v[k]) {
          t = v[j];
          v[j] = v[k];
          v[k] = t;
        }
      }
    }
    for (l = 1; l <= i / 2; l = l + 2) {
      v[l - 1] = (v[l - 1] + v[l]) / 2;
      v[l] = 10000;
    }
  }
  printf("%.1lf\n", v[0]);
  return 0;
}
