#include <iostream>
#include <cstring>
#include <vector>
#include <set>
#include <map>
#include <sstream>
#include <cstdio>
#include <algorithm>
#include <stack>
#include <queue>
#include <cmath>
#include <iomanip>
#include <fstream>
//#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = (1 << 30);
const ll inf = (1LL << 60LL);
const int maxn = 1e5 + 10;
int n;
int arr[maxn];
int main(int argc, const char * argv[]) {
ios_base::sync_with_stdio(false);
cin >> n;
for(int i =0 ; i < n; i ++){
cin >> arr[i];
}
sort(arr, arr + n);
double ret = ((double)arr[0] + (double)arr[1]) / (double)2;
for(int i = 2; i < n; i ++){
ret += (double)arr[i];
ret /= (double)2;
}
printf("%.4f\n", ret);
return 0;
}
