#include<bits/stdc++.h>
#define rep(i,n) for(int i=0; i<(n); i++)
using ll = long long;
using namespace std;

int main(){
    int n;
    cin >> n;
    double v[n][n] ={ {0.0} };
    double input[n];
    rep(i, n) cin >> input[i];
    sort(input, input+n);
    rep(i, n) v[0][i] = input[i];
    
    int cnt=1;
    int d=0;
    while(n>1){
        d=0;
        for(int i=0; i<n; i+=2){
            if(i==n-1){
                v[cnt][d++] =  v[cnt-1][i];
            }else if(v[cnt-1][i+1] != 0.0){
                v[cnt][d++] = (v[cnt-1][i] + v[cnt-1][i+1])/2.0;
            }
        }
        n = d; 
        cnt++;
    }
    cout << v[cnt-1][0] << endl;
    return 0;
}