#include <bits/stdc++.h>

using namespace std;

#define forsn(i, s, n) for(int i=s;i<int(n);i++)
#define forn(i, n) forsn(i, 0, n)
#define all(v) v.begin(), v.end()

typedef long long tint;

const tint MOD = 1000000007;

int main(){
	int n; cin >> n; vector<double> a (n);
	forn(i, n) cin >> a[i];
	sort(a.rbegin(), a.raend());
	while(a.size() > 1){
		double x = (a[a.size()-1]+a[a.size()-2])/2;
		a.pop_back(); a.pop_back();
		a.push_back(x);
	}
	cout << a[0] << endl;
}

