#include <bits/stdc++.h>
int main(void) {
  char str[1024];
  int N, i, j, k, im, jm;
  double v[1024];
  double min;
  fgets(str, sizeof(int), stdin);
  sscanf(str, "%d", &N);
  for (i = 0; i < N; i++) {
    scanf("%lf ", &v[i]);
  }
  for (k = 0; k < N - 1; k++) {
    min = 99999.9999;
    for (i = 0; i < N - 1; i++) {
      for (j = i + 1; j < N; j++) {
        if (min > fabs(v[i] - v[j]) && v[i] != 0 && v[j] != 0) {
          min = fabs(v[i] - v[j]);
          im = i;
          jm = j;
        }
      }
    }
    v[im] = (v[im] + v[jm]) / 2.0;
    v[jm] = 0;
  }
  for (i = 0; i < N; i++) {
    if (v[i] != 0) {
      printf("%f\n", v[i]);
      break;
    }
  }
}
