#include<bits/stdc++.h>
using namespace std;
signed main()
{ 
  double n,a[2100]={},b;
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>a[i];
  }
  sort(a,a+n);
  b=(a[0]+a[1])/2;
  cout<<(b+a[2])/2<<"\n";
}


