#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
typedef long long ll;
const int MOD=1e9+7;
const int MAX = 1000000;
const int INF = 1e9;
const double pi=acos(-1);
using namespace std;

int main(){
  int n;
  cin >> n;
  vector<double>a(n);
  rep(i,n) cin >> a[i];
  sort(a.begin(),a.end());
  cout << fixed << setprecision(5) << (a[n/2]+a[(n-1)/2])/2<< endl;
  
  return 0;
}